Which is why they offer a Repair option if you boot the CD. Try that.
I had some problems with my display drivers so I uninstalled them. When I restarted my computer it would not boot properly and said there was a file missing. I used XP disc to try and run a repair. The process did not complete and now I'm completely stuck. Every time I restart it tries to resume the install but it can't boot up normally and then it goes to safe mode and I get an error "windows xp setup cannot run under safemode? and I have to restart. I cannot cancel the install or get into Windows at all. I have tried hitting F8 and starting in safe mode or safe mode with command prompt and the same thing happens. I have tried booting directly from the XP disc and no luck there either. If nothing else works I will just install my hard drive into my other computer as a slave and get all my documents and then format the drive and re-install on my other computer. But I would really like to salvage this install.