Due to Disk Doctor i cannot boot anymore!

hi I’m using symantec disk doctor 2004 on windows xp pro sp3, in order to check the disk (I usually do it regularly with all the other programs in the suite) as required by the program I planned the operation....then rebooted, the point is that since then I cannot boot anymore. After I started the pc, the diskdoctor starts his scan, once he finish (without detecting any error) it just reboot the machine again (instead of logging to windows)...same process again and again

 

I also tried to stop him from doing the scan (by pressing a key) but it just show me that he is stopping the scan instead of quitting himself

 

what i can do to cancel this process from the boot? (i can use the XP recovery console if needed)

 

Regards, Nicola