stumped

[augustorm]

Hey peeps,
I'm having some probs with one of my machines.
One day I pulled a memory board out to compare to one that a friend had given me. I saw that they were not the same so I put mine back in and gave the other one back to my friend telling him that I could not use it with my MB.
I go to boot my machine and everything looked normal...everything until windows tried to load....just when I think I am going to get the Wallpaper and my network logon, the machine just shuts down.
No error msg, nothing, it is as if I myself had chose the shutdown option.
So, I've been troubleshooting for about two weeks now and finally I see a error msg during the autoexec.bat screen that says: "Memory manager not found". and it then it refers to EMM386.
The thing runs in safe mode all day long....but when i choose normal boot, it shuts itself down.
I have reinstalled windows. I have not reformatted yet.
Maybe its just time for a better machine.
I have wanted to see for myself if amd processors are better for game play.
This is my game machine that is having the probs.
So, think it could be perhaps a virus doing this or perhaps my powersupply. I just dont get it.