ScanDisk can't finish

I usally ScanDisk & Defrag every 7 to 10 days.
Now ScanDisk cannot finish cuz something is searching my HD
in the background. The HD starts clicking about two
minutes after no activity all the time now even when I
close everything except Explorer and Systray.

No programs are on automatic. All or set to manuel.
House cleaned using, MS RegEdit, Spyware
Nuker,PC-PowerScan, McAfee, Task Manager to off, etc.

Once got a error msg that "resources were dangerously low,
do I want to close MOSEARCH ?"

What is Mosearch & what does it do & do I really need it
for Win98SE ver. 4.10222A, 128MB RAM ?

Thanks in advance,
James.