BSOD when logging on to default drive

I have Windows XP installed on two partitions of my computer system. The Drive K: is the default drive while Drive C: is a fall back option if Drive K fails to load. But now when I try to log to the default OS, it throws a blue screen error message and redirects me back to OS choice window. I have tried to repair it by running Chkdsk/r, boot using Safe Mode, scanned for viruses using AVG 2012 and also used MalwareBytes to scan the Drive K: but I am still receiving the same error. What shall I do resolve the issue?
