[RESOLVED] Scandisk and Defrag hang

My config is the following:
Pentium II / Windows 98 / HDD 8.4 GB IB / Mem 64MB
Partitionning: C: 1.5 GB / D: 5GB / E: 1.5GB
I use Start => Pgms => Accessories => system tools => scandisk or Defrag
When I start SCANDISK using the "Standard" option ==> OK, No error
When I start SCANDISK using the "Thorough" option ==> Scandisk runs
for a while then hangs (i.e on system files cluster 1569, but can be
another one in the data files clusters...)...
No HDD activity. Pressing "CANCEL" button has no effect..the system is
frozen, NO action allowed...The only way to recover is to delete the
task using Ctl+Alt+Del...And most of the time, I got a blue screen with
the msg "System is unstable, restart your computer"...
Power OF/ON the is the only way to restart the system...
I ran the "system files test" several times which completed successfully
each time...
Note 1: I got the same pb with DEFRAG which hangs after let's say 2 or 3
minutes...Displaying 10% in the Defrag dialog box..with the same
symptom and same recovery as described above..
Note2: Appart of this, my computer is running fine without any pb...
Any hints, please???
Thks and regards

hi,before running these 2 programs make sure you disable any screensaver and antivirus,if you don`t it will lockup your pc everytime
Clauded

boot to a command prompt only and run the command line versionf of scandisk. This can sometimes do things that the windows version cannot because it runs in a non-multi-tasking environment.

yes, and the defrag in win98 takes forever..often looks like its hung up around 10% for a long time, but does eventually start moving again..try giving it more time

From the CLAUDED suggestion, I disabled (stopped) an automatic antivirus pgm that
was running and it seems that the pb is fixed
DEFRAG is running fine and Scandisk (thorough) as well..
Defrag keeps running even if the screensaver is active...I even try to do some actions
like selecting "Control panel" then "Display"
then changing the screensaver parameters...
while defrag was running...It didn't affect
the pgm and defrag continued to run...
Thanks a lot to all of you...
PS: Answer to JEANNED:
The first time I got this pb, in fact I started defrag, I watched it some minutes then I leaved my home for several hours... When I came back home, the status was
unchanged (same cluster displayed)...
Anyway thanks a lot for your help...
Thanks also to Bdunn...
Have a nice day...