What shows on your screen after to BIOS load?
Is there a message such as: "NTLDR is missing?"
There should be some message on the screen. From that, one can begin to diagnose the problem. You can also boot from you Windows XP CD and do an "in-place" repair [2nd repair option], which can resolve your problem. The improper shut-down possibly damaged your NTFS [Windows NT File System].