Help, i dont know what to do anymore

im having problems with my computer, it runs really slow and i thought it was a ram problem but i got new memory and it still is doing the same thing, somtimes it crashes also only if i run like 5 windows at the same time though. its nearly impossible to do anything that isnt just text, like videos, games ect. i cant do cuz its just to slow. please help i really dont have any more ideas anymore

o also, ive defraged many times used regertry cleaners, reformated multiple times and checked for viruses and spyware and none of it has helped

thx for the help

First. Get memtest and then either burn it to a CD or (preferably) install it to a FLOPPY. This will test your memory.
Then go into BIOS settings and try to underclock proccesor. Then make sure to check temperature of proccesor, hard drive, voltages and so on. What power supply you have?

Give us more info.

i ran memtest for a few hrs but everything cleared, im going to run it over night today though.
im not exactly sure what power supply i have, ive forgotten, i build my computer too long ago to remember.
i comp is pretty new i built it a year ago or so, im running 2 sticks of 1g memory 800mhz, my comp stays plenty cool there are many fans and the heat sink on the prosescer is incredible and keeps it very cool. i dust my comp with compressed air on a regular basis so its clean.
i will check my video card and power supply and tell u what both of those r.
if u need anymore info please ask

thx for the help

This could have nothing to do with it but what anti-virus do you use? In all likleyhood it is not as good as AVAST (FTW!!!)

if we can rule out that it is a hardware problem I would suggest you install avast and disable your current anti-virus (just for a bit)

Avast will run a very thorough check of your system to make sure you are not infected with anything. That check should find most things if they exist. (Just another option)

ive been runing mem test for 2 days and there have been no errors, my memory is fine. its doubt its my anti-virus i have avg and its been working fine