Problems with booting after running chkdsk.

Whenever I run CHKDSK /f on my boot drive. The system takes ages to boot up (over an hour to get to the login screen, and then another hour before the desktop starts to appear.) Using different logon’s does not help.
It the give me a blue screen, not the classic blue screen of death with error messages, just a blue screen with “STOP: unknown hard error” in the top left corner. Sometimes there is an error code that is not listed by Microsoft.
Rebooting and doing a restore works.
The chkdsk reports no problems
I am running WIN XP PRO SP3.
I have run antivirus/spyware checks and found nothing.
I am running the latest drivers on everything.
I have also checked the memory by running MEMTEST.
Any ideas?