My SuSE Linux is very slow sometimes.

Dear my friends.... I wonder why my SuSE Linux 8.1 becomes very slow sometimes. It becomes slow if my harddisk suddenly being busy because of an unknown process. I guess because fsck but I am not sure. What is the unknown process actually? And how can I stop /cease it ? Thank you very much in advance. __________________________________________________ Do you Yahoo!? Yahoo! Tax Center - forms, calculators, tips, more http://taxes.yahoo.com/