!somebody hacking my PC,HELP

[yuli]

My PC connect to internet through cable modem, this few days, something strange 
happened, my PC running Win2000, harddisk always read and write, I had share some 
directory, and when I disconnect the sharing, error message "1 files opened by ....."

How should I know any attack and trace the illegal attack, like any file log to show 
the attack?

any protection can recommend.

thanks in advance

please email [EMAIL PROTECTED]