i bought a computer from a friend. i started having problems of crashing. is there one way to clean all spyware and correct registry errors? i'm using most of the programs from download.com. windows washer, windows reg. repair. spy doctor etc. i have no use of the crtl, alt, delete when my pc crashes.????

What exactly happens when it crashes? Freeze? Restart?

If restarting change this setting:
rt. click My Computer then click Properties then Advanced then Startup and Recovery Settings then unclick Automatically restart

Post the exact error message on the next crash.

If freezing (no mouse or keyboard response):
Look in your Event viewer: rt. click My Computer then click Manage then Event Viewer.
Or: Administrative Tools/Event Viewer or Start/Run/ eventvwr
Open the system as well as the application tabs & look for X errors. Click error line for details.
Post back the source & event id especially of errors that seem to coincide with a crash.

There is no one way to maintain your system. The programs you mention are fine. My own free favorite is CCleaner:
http://www.ccleaner.com/

To check for any malware issues:
Please follow the instructions HERE & then post your log in a new thread in the Spyware, Adware, Viruses and HijackThis Logs section.
(Not in this section please).