Well, does your laptop still bluescreen if you connect your N900 via mass storage? If it doesn't, then it's easy.

Just hook up the N900 via mass storage.
Then you will see 2 new drives in explorer. (eg. F and G drive)

Now go to command prompt in WIndows. (Start - Run - type "cmd")

Then run:

chkntfs f:
chkntfs g:

This just checks for the dirty flag and will tell you which one is set.
Then run:

chkdsk f: /f
chkdsk g: /f

(depending on which drive letter is said to be dirty)
Once the chkdsk completes, it will clear the dirty bit.