How can I remove the problems of my PC?

Hello,
Please help me in sorting out my problems.
1. When I switch on my PC, two windows appear namely C:/Windows/system32/winxp.exp. after few seconds there appears a box saying illegal instruction and all these closes down.
2. I installed AVG, Avira, and finally Kaspersky Anti-Virus 2009. But when I open them the same problem appears. The same window namely C:/Windows/system32/winxp.exp appears and another window of illegal instruction comes and closes down. Finally, these anti-virus softwares doesn't work.
3. In my Computer, when I double click C:/ or D:/ ,there appears a box called choose program to run with(Auto Play). But these open when I explore.
Please do help me in solving these problems.