how to scan when computer won't boot

[mach4]

my inspiron 5000 goes through the dell screen and specs but when it enters the windows 2000 professional screen, the status bar goes about half way across then a blue screen pops up with a stop error message.  It recommends running a virus scan and CHKDSK /F but I don't know how to.

HELP!

Thanks.

[Lisandro]

Trying to do this in Safe Mode.
SafeMode booting (repeatedly press F8 while booting): http://support.microsoft.com/default.aspx?scid=kb;en-us;315222

Can you schedule a chksdk there.
Instructions - Go to "Start", "My Computer", right-click on the "C:" drive, left-click "Properties", select the "Tools" tab, click "Check Now...", check "Automatically Fix File System Errors", then click "Start", "Yes" and Reboot. Repeat this for any other hard drive partitions in your system. Only the drive partition with Windows installed will require a reboot.

If you succeed... then you can schedule a boot time avast scanning...