Well, I have seen some wide spread reports of Fragmentation taking on your performance problem... Even though NTFS is supposed to be the "fastest" way to address disks...*snicker*

Get a GOOD defragmenter (even Norton Systems Works would really do, using Speedisk)

You should see a TON-O-IMPROVEMENT.

I am guessing that the SP6a you just installed just fragmented the SCHNOTT out of the FS. Heck even Fresh installs of W2K are as much as 35% fragmented. NT4 never really checked. NT3.5x was assumed you had to defrag every so often.

Good luck.