http://support.microsoft.com/kb/314477

eta: that error appears to not be a vista error. your mbr is probably fucked.

can you or can you not risk damaging your current file system? either way, you should backup before doing the following if you have irreplaceable data on that partition.

if you have data that you can lose, run a recovery disk and/or recovery partition

if you have irreplaceable data and do not want to take the hassle of backing up then recovering, you can try this. http://support.microsoft.com/kb/927392

if that doesn't work, try this http://vistasupport.mvps.org/windows...ir_options.htm

if that doesn't work, recover or backup then recover depending on your situation based upon the aforementioned question.