Yeah be specific.
Not a Vista user, but i think if you start up tapping F8(?) it MAY take you to the command line, from there type in chkdsk -f, this should check the volume and fix any errors.
Or, again hold F8 on startup, go into Startup Repair (it may not be there) then follow this-
On the Advanced Boot Options screen, use the arrow keys to highlight Repair your computer, and then press ENTER. (If Repair your computer is not listed as an option, then your computer does not include Startup Repair as a preinstalled recovery option.)
Select a keyboard layout, and then click Next.
Select a user name and enter the password, and then click OK.
On the System Recovery Options menu, click Startup Repair. Startup Repair might prompt you to make choices as it tries to fix the problem and, if necessary, it might restart your computer as it makes repairs.
An exact error or an error code would be ideal