My suggestions......
1. Use a meaningfull title for your post. "Help!" tells us nothing.
2. "Nothing works anymore" is not specific enough.
3. Get into Safe Mode (press F8 during startup and select Safe Mode form the startup menu) and run the maintenance.
4. Reboot into normal mode and run whatever AV you have. If you haven't got one then you were asking for it.
5. Get an updated version of an AV on a pal's comp and then upload it to yours and run it.
6. Don't panic! Just be very worried. And post back let us know how you got on.
HTH mc