My computer's RAM potential

4GB is the limit.
the 531 board only has 4MB of VRAM which kinda restricts it from running up to it's potential.
4GB of DDR2 800MHz is the absolute limit..
4GB(2x2GB) in slots 1 and 2 (farthest away from the middle) is the configuration for dual channel mode.
just populate those two slots with 2GB sticks and you will be set.

let me know if you want cpu, video, processor and powers supply upgrade info..

changing your psu to run what what kind of gfx card.?
see here's the thing, the 531 can only run an higher end OLDER dual core amd athlon 64x2 and it maxes out @ 3.1GHz Brisbane and 3.2GHz Windsor.
those chips are not strong enough to push a higher end gfx card like a GTX470 or better, you will have a bottleneck.
and without any overclocking in that unit, to be honest a GTX460 might be pushing it..

so upgrading the power supply to run what gfx card.?
it's really not logical to do so.
the Dell OEM power supply for your unit is 300-watts and Dell OEM psu is actually stronger than listed or labeled..
and physical dimension wise I do not know if you can fit a dual slotted gfx card.
keep your Dell power supply and just get an ATI HD5670 and roll with that, my recommendation.
the HD5670 calls for a 400-watt system but don't worry about that, it will run on yours now.
guarantee it.
becuase soon it will be time to build new or look for newer unit..

and by the way, you do not want a eco green power supply.!
if anything get a real ATX psu like Corsair Builder's Series 430-watt..
but that will be for future reference..

I don't do green power supplies...

so you're saying theoretically that if i can fit a dual slot graphics card in and a bigger psu then it could be worth it, but you'd recommend an nvidia so it matches my chipset?

http://www.pacificgeek.com/product [...] 531-1C.jpg

here's the back of my pc, i think that it can fit a dualslot graphics card in, i'll open mine up tomorrow and take a photo to upload so you get a better picture. i've looked on a few links n i think it might be best for me to measure the dimensions of my current PSU too.

SO, if everything were to work out size wise, how much would my processor limit the usage of a decent graphics card like the hd5750?

I forgot they started making some single slot higher performance cards..
examples:
http://www.newegg.com/Product/Prod [...] -_-Product

this will definitely take away the worry of it physically fitting.

take it as a sign of fate becuase you didn't want that RAM anyways...
you want PC2-6400 DDR2 800MHz CL5.

tell you what I'm going to link how to max your unit out, give me some time and check back.

P.S.
looks like the dual slotted card will fit.

In the UK right.?
http://www.amazon.co.uk/G-Skill-PC [...] B000RJH32C

1.) http://www.amazon.co.uk/AMD-Athlon [...] B003Z96YA8

2.) cooler is not necessary just an example of what you can do with this unit and the 521 as well.
just if you do the cpu upgrade use AS5 thermal paste or better and you will have no problems.
3.) yes, crazy massive step-up from x1650.
4.) it will run DDR2 667MHz, again I'm just showing you the maximum that you can use.
even if you run windows 32-bit OS then 2GB of DDR2 800MHz can work for now.

cool cool, i think i'm finally cracking down on my problems haha.

OK so...

1) which is better, the ati hd 5670 or the 5750?
2) i'm correct in thinking neither will require a psu upgrade?
3)http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=190403540640&ssPageName=STRK:MEWNX:IT

i've bought these RAM, they've arrived, but the PC won't boot and just beeps when i put them in, they seem v compatible if crucial is to be believed:

http://www.crucial.com/store/listp [...] iron%20531

any ideas why this might be happening?

yes, because you need this instead..:
http://www.amazon.co.uk/Kingston-T [...] 531&sr=8-7

timing - speed - latency...
I know for the fact that DDR2 800MHz CL5 5-5-5-18 will work.
I use them in mine..

No, I do not recommend it unless you have a LGA775 chipset and you have AMD so do not mix.
a little info for you.

AMD uses something called an IMC (Integrated Memory Controller).
It helps the AMD chips perform very well in memory related tasks (because now the ram isn't controlled by the motherboard through the FSB)
but it also has a few quirks.
The IMC doesn't seem to like a lot of stress, and so in general, you wont get as much of an OC out of your ram if you have all of your ram slots populated.
So it should be easier to get more performance out of only two sticks of ram.

*Intels Nahelem architecture utilizes this same design, leaving the Core 2 series as the only mainstream processor to still use the FSB design.

Also, the same thing goes for mismatched ram, the IMC just doesn't like it.
So if you have ram that is not from the same kit, and are experiencing instability, try taking out the non-matching set, and see if that helps out.

Also, you might have heard about the “timings” of the ram, and how that is important.
I have seen a lot of people get confused with that.
Let me explain this as simply as I can.

There is memory speed, and then there are memory timings.

Speed is the frequency that the memory operates at (in MHz... and remember that when you are looking in CPU-z that ram is DDR [Double Data Rate], so the frequency that it says will always be half of what it is actually running at). It is fairly straightforward and easy to understand.
And remember that the ram speed is tied to the reference clock, and in this way you can easily OC your ram beyond the stock speed.
Speed is mostly important for higher bandwidth, as it just means that the ram can move more information.

Timings are different, and should not be confused with the speed. Timings do not effect the speed (in MHz) of the ram at all.
Instead, they change how “efficient” the ram is. In other words, the timings affect the “turnaround” of the information.
The timings are generally listed something like this: 5-5-5-18. While I wont go into all of the details about what those each mean here,
I can give you a basic idea of what the timings mean. Timings change how long the ram will wait to do something.
So having ram with looser (numerically higher) timings, means that the ram will “wait” longer in between processes.
Using the example of 5-5-5-18 ram, information is copied, it then waits for 5 clock cycles before it moves onto the next step.
Ram with 7-7-7-23 timings running at the same speed (in MHz) will move the information there just as quickly,
but then will need to wait for 7 cycles between doing things, rather than 5.
This is why “performance” ram is in fact faster.

the higher the MHz the faster the RAM and the lower the latency the quicker the RAM..
I do not recommend the HD5750 if you are getting a power supply.
I recommend the GTS450 for your unit...! nVidia like your chipset..
and any psu up to 500-watts (don't need that much, even a 430-watt Corsair Builder's Series psu will work) just make sure it has the 6-pin power plug or two..

for you the GTS450 for a few reasons why IMO..
performance wise it's the HD5770 equal and also adds CUDA and other nVidia bonuses, plus it's your motherboard chipset.
as for power supply, I try and find a specific one for you.

cool cool i think i'll go with your recommendations,

with regards to the PSU, on the link it says:
Product Dimensions: 40 x 25 x 20 cm ; 2.6 Kg

surely that can't be correct?

Inspiron 531 power supply specs:

Power
DC power supply:
Wattage
300 W
Maximum heat dissipation
162 W

NOTE: Heat dissipation is calculated by using the power supply wattage rating.

Voltage (see the safety instructions located in the Product Information Guide for important voltage setting information)
115/230 Vac, 50/60 Hz, 7 A/4 A
Coin cell battery
3-V CR2032 lithium coin cell

Physical Height
36.2 cm (14.2 inches)
Width
17.0 cm (6.7 inches)
Depth
43.5 cm (17.1 inches)
Weight
12.7 kg (28.0 lb)

going to cross-reference some power supply dimensions.. BRB.

that link says it's 300w, i'm pretty sure i already have a 300w psu?

http://cgi.ebay.com/DELL-Inspiron- [...] 5881bed690
350-watt
DELL G849G 350W Power Supply

it's good and the manufacturer of the 350-watt power supply US version is LiteOn, good solid maker..

YES..!
and were also talking about a Dell certified psu it can handle heavier cards than that..

no problem, enjoy..

I'll look, hold on..

http://www.amazon.co.uk/Kingston-K [...] 183&sr=8-2

so something like that?