Does not boot from Windows

I downloaded Knoppix 3.3 from www.knoppix.com.
I booted my computer from the CD-ROM and Knoppix started. It seemed like it works good. After some use I shut it down and tried to boot it from Windows XP, as always. But the Computer does not respond at all. Screen is totaly blank and I can not do anything. Does not boot from CD-ROM or disk drive. It does not give any message on screen.
I tried to boot it from my original Windows Cd but it seems like it does not even read the CD.
Could you help me please?
Thanks.

If it's a Dell there's a known issue. Do a search here for Dell.

If it's a Dell Machine, pull the plug, push the power button with the cord disconnected, reconnect power and it should boot as normal. There is something about the BIOS on some Dells that causes this.