[TippeX]

same happens in safemode ? (idea is to see if its a driver issue)
i had a similar thing - serious 'lag' between windows boot -> login screen (and even after...), turned out to be a screwed partition on the drive..
so that could be 1 reason, other possible cause is sptd.sys (if you use daemon tools or alcohol..) - its been known to have problems in the past...

first step would be to boot with the windows cd/dvd, and run the recovery console and chkdsk the drives, chkdsk /r (i think) repairs the drive... regardless... takes longer but theres nothing more annoying to run chkdsk, then be told theres errors, and then having to run it again with the /r switch...

ntldr missing is definately a symptom of something going screwey on the drive..