Adding more RAM slows my PC

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If by chance you added an ECC stick then sure. Further, mix-matching RAM isn't a good idea either, you could be throwing a ton of errors.

Q - What RAM? Please provide links to all of your RAM.
Q - What MOBO?
Q - What CPU?

Umm I have no idea what ECC means or stands for. As for what ram? u well I don't really now how to find out so I'll just type in what was written on the stickers.
My original stick is an OCZ 2GB 5-6-6 @1.8V (IDK what those numbers mean)
The new RAM is a CORSAIR 1GB...that's all there was on the sticker..(also I think this is worth mentioning the "new" RAM is not really new I got it from my old PC)

As for MOBO I have a GIGABYTE G31M-ES2C and a Pentium R Dual-Core 2.6GHz E5300

GA-G31M-ES2C (rev. 2.3) - http://www.gigabyte.us/products/product-page.aspx?pid=3...
Specs:
2 x 1.8V DDR2 DIMM sockets supporting up to 4 GB of system memory
Dual channel memory architecture
Support for DDR2 1066(O.C.)/800/667 MHz memory modules

Manual:
Due to chipset limitation, read the following guidelines before installing the memory in Dual Channel mode.
1. Dual Channel mode cannot be enabled if only one DDR2 memory module is installed.
2. When enabling Dual Channel mode with two memory modules, it is recommended that
memory of the same capacity, brand, speed, and chips be used.

BIOS:
Intel Pentium Dual-Core E5300 2.60GHz 2MB Wolfdale 45nm R0 65W 800 FC

The above is for reference. As I suggested, it's not a good idea to mix-match RAM. ECC means error correcting memory; you cannot mix ECC with non-ECC. Further, in order for 'Dual Channel' to work both DIMM slots must be equal is capacity (size -- GB); 1GB + 1GB or 2GB + 2GB vs 1GB + 2GB (bad).

Since you don't have the information handy, you'll need to either upload the following images or on the 'About' tab in CPU-z save the TXT file and paste the following information:

1. Memory SPD < through / (stop at)> SPD registers, and
2. from below all of the items in 'blue':
CPU-z - http://www.cpuid.com/softwares/cpu-z.html

Wow first of all thank you for taking the time writing that monstrous reply  

And there's the pic. Thanks for the link by the way " alt="" class="imgLz frmImg" />

Okay, above was Item #1, I still need the 'SPD' tab data for each stick -- 1GB and 3GB.

Oh sorry there's one
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and the second

Okay, below is a comparison to the calculated MIX and what the BIOS set the RAM. Clearly, whic is rare they match. Regardless of what the Memory tab shows the RAM is not running in Dual Channel mode (a CPU-z bug). I looked in your manual and about all you can set is the voltage (+0.10v) and the Frequency (Memory Multiplier).

DDR2-667 5-5-5-15 @1.80v
DDR2-667 4-5-5-15 @1.80v
====================
DDR2-667 5-5-5-15 @1.80v ; MIX

DDR2-667 5-5-5-15 @1.80v ; BIOS

What I would do next is to create a bootbale CD/DVD of Memtest86+, use the ISO/zip file, and run it for at least 4 full passes.

If there's any errors then you options are limited, and if it were me I would purchase a matching set of 2x2GB - http://www.newegg.com/Product/Productcompare.aspx?Submi... and probably the Mushkin.

Problem, OCZ doesn't produce RAM any more and the 1GB is too small as 2x1GB. It's probably either errors or the mix-match itself. See how the testing goes and let me know. I'm going out for a few hours...Wrath of the Titans.

Well I haven't really spent much time on the BIOS other then OCing my CPU.
And are you saying the two sticks match? I didn't get that one...

So....I need to set the voltage a little higher and increase the Memory multiplier. Ok how would I know that the frequency is identical in both sticks?
And that last part with the bootable CD/DVD if you would so kindly explain again
Oh and I read at IGN that "Wrath of the Titans" is crap....but then again...it's IGN....go figure...looks really nice to me

The BIOS seems to be setting the Frequency and CAS Timings correctly. Unfortunately, it seems the underlying issue is mix-matching, and/or errors. I stated for you to run Memtest -- "run it for at least 4 full passes."

If it were 'my' PC I'd purchase a matched set of RAM; I linked some affordable and good kits.

Manual:
Due to chipset limitation, read the following guidelines before installing the memory in Dual Channel mode.
1. Dual Channel mode cannot be enabled if only one DDR2 memory module is installed.
2. When enabling Dual Channel mode with two memory modules, it is recommended that
memory of the same capacity, brand, speed, and chips be used.

So Mushkin Enhanced Silverline 4GB it is....I'll get it as soon as I can. Thank you for your help.
And should I remove the 1GB stick until I get the new 4GB? Because it will take some time ordering and stuff...

That's what I would do, if the 1GB cause the slowdown then remove the problem.

One thing that I would do first, thinking about it, is to try the 2GB in both DIMM slots and compare -- just to make certain it's not a DIMM, Channel or CPU issue...

Got it...well you've been a great help to me thank you very much.

Wow this was unexpected...I switched the ram sticks with each other and all of a sudden the game runs fine....may I ask why the hell is that? and once again...thank you

Possibly how the BIOS is reading 'SPD' information, and it's probably looking at one DIMM and setting the parameters. I've seen this before which is why I recommended swapping to rule-out compatibly or something else.

Depending on the 'Game' 4GB is recommended and some games even benefit from up to 8GB.

If you're satisfied then there's no reason to make further changes...