What the hell is the matter with XP

Ok here's the problem, I just put 512 Meg in my machine, and now it's acting like I only have 64, my applications are lagging, everything is acting like it takes five minutes to think about it before it does anything. Anybody had this problem, or are my not configured right?
Thanks for the help.

try a fresh install.

Hmmm...that's odd, it shouldn't slow down like that. Take the new ram out and see if things go back to the way they were.

Also, list yer specs if you need more help.

Trohbock, list your setup, mainly hardware, and perhaps we can do more.

In the meantime, off the top of my head:
- if an older mobo (Via MVP3 chipset?) you would need more mobo-based cache memory (L2, 2meg, I believe) to be able to work with 512meg of system memory. Otherwise, symtoms are exactly what you describe.
- Check the memory in another machine.
- If you mean 512meg in one module, even some recent mobos balk at it.
- Along the same lines, some of the best-priced memory out there may be compatible only with several Athlon mobos but not with Pentium/Celery ones.