Ok, my first time posting here, hope i get an answer. I have a IBM NetVista Motherboard P4 with 256 MB(2x128 MB) installed. Since the computer was somewhat slow, i decided to add more RAM. So i installed a 512mb + 256mb and left one of the 128mb. I installed the highest RAM closest to the CPU and then the lower ones. I also checked the Task Manager and it showed that i have 896MB RAM. Now, the computer seems to be running slower than before! What is the problem? P.S. Formatting is not an option for me. Not too may Services + Startups Programs open up when i start the computer, and i only have some documents in my Hard ( 5GB Used out of 40GB)

the slower ram may be hanging the faster one up try taking the smaller of the two out look up the memory compatability chart and see if the two are compatable aslo are you useing ddr2 ram or old 133 , 100 ram they should be same if you want speed

They are PC133 SDRAM. So you are saying that i need 2 x 256 or 2 x 512 ?

Look at your manual. I think your board may utilize dual channel memory mode. If so, you need to have the same amount of RAM on each memory controller. Your manual should explain.

Don't have the manual. Now if i decide to just leave one ram of 512MB in it, it won't matter if the board supports dual channel or not, since i will only have one RAM, correct?

You think the computer is running slower than before, with more RAM. I was giving you a possible reason. It isn't that the computer won't run in single channel, it just would be slower. I don't know for sure your rig even uses dual channel. Did you unplug the computer before messing with the RAM?