well,,something must have changed. Did you just install
SP2? What is probably happening is that windows is
crashing at start up. NT4,2000 and XP, by default,
automatically reboot when they crash (blue screen)and
since is crashing at startup it will immediately reboot
into an endless loop. This is a known issue with a
particular piece of spyware (TV Media) that may have been
installed on your computer before SP2 was installed.
Basically SP2 breaks the spyware and the result is exactly
what you describe. This is one of the biggest issues
regarding SP2 and has been addressed by Microsoft.
You will need to cut and paste this URL to visit the KB
article
http://support.microsoft.com/default.aspx?
kbid=885523&product=windowsxpsp2
To confirm that you are getting this exact issue, you will
need to follow the instructions in the "SYMPTOMS" section
of the aforementioned URL. Once you have confirmed that
this is indeed the problem you are experiencing, you will
need to follow the instructions in the "MORE INFORMATION"
section of the aforementioned URL. If this is beyond your
skills (using recovery console) you will need to get your
computer to someone more experienced. I advise you ring MS
tech support, since this is a spyware related issue, they
SHOULD NOT charge you.