RAM UPGRADE HELP!!!

I'd go with 4GB of the 800Mhz, over a lower clock speed and more ram.

Your going to want something with a low CAS and good memory timings. (a CAS of 4 and timings of 4-4-4-12 are probably the best you'll see for this type of memory).

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

Though to be honest, I doubt you'll be able to tell the difference between the two, below is a CAS of 5 and timings of 5-5-5-15. It's $25 cheaper. Besides it's not like your going from DDR2-800 to like DD3-1600 or something where you'd be able to see the difference, but it's your money.

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

What OS are you running? If Win 64 bit go ahead and upgrade to 8GB but if you have Win 32 bit upgrade to 4GB ONLY ( 32bit system can utilize only 3GB so there is no point of getting 8Gigs)

i have windows ultimate 32bit but i can upgrade to 64 withouth a problem i currently have 4GB of 667mhz

Another thing is that your motherboard may not support 800Mhz 2GB modules
http://www.dell.com/downloads/global/products/optix/en/...

so to be on safe side get 2x2GB 667Mhz stics in a case you are running Win 32bit
http://www.tigerdirect.com/applications/SearchTools/ite...

If you run win 64 bit get the same but 2 pairs...just a word of caution...older motherboards may act weird when all memory slots are occupied...well it is just leap of fait you have to take

Good luck

Max

Well then upgrade to 64bit and get another 2x2GB and you have 8 gigs...don't expect to see significant if any changes...If I were you I would just build new rig and salvage whatever you can from your old one.

which is the best ram brand i can buy?

because im thinking about buying this ...

http://www.newegg.com/Product/Product.aspx?Item=N82E168...

i also found this ....

http://www.ebay.com/itm/G-SKILL-4GB-2-x-2GB-240-Pin-DDR...

which i think im going to get 8GB of this since its 667mhz

The spec sheet says it supports 800Mhz and up to 8GB max mem. THAT IS UNLESS you have a ULTRA SMALL FORM FACTOR 745. That model only support 667Mhz. Which version do you have?

http://www.dell.com/downloads/global/products/optix/en/...

Look at the module types supported...it specifically writes "2-GB (800MHz not available in 2GB DIMM)" meaning that at the time the board was released 2Gb modules were not on the market =>therefore it does not support them...you grew up in USA so you better start reading/understanding small print  

this one is better it has Heat Spreaders which should help with cooling