Hi, I have been dual booting XP pro and Vista Ultimate for a few months without problems. The other day I got a virus (b104.exe) that left me unable to boot up - I couldn't even get to safe mode. I managed to get into Vista by changing which HD boots up first. However, everytime I want to boot up now I have to go via F9 and choose the secondary boot up device as otherwise I get an error "NTLDR is missing." I know this is an XP componant but I no longer have the XP disk to do a repair. How can I get my pc to think that Vista is the only OS on the PC WITHOUT formatting the drive with XP? Thanks.

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And you might want to rethink how you do dual booting for this reason next time. You could have setup the dual boot by having each OS on separate hard drives, and manipulated which OS you boot to using the hard disk boot priority. That way, you avoid these kinds of scenarios whether it be due to a virus attack, a hard drive failure, etc. "Enough, enough bowing down to disillusion! Hats off & applause to rogues & evolution! The ripple effect is too good not to mention. If you’re not affected, you’re not paying attention!"

Since you are able to boot into VIsta - install VistaBootPro or EasyBCD 1.6 & use either of the two programs to install a Vista boot loader on the Vista HDD. Another thing you can try if you have your Vista DVD is Vista's startup repair though this option is longer.