Thanks for all replies.
Yes i have latest version of spybot with all updates.I get a complete freeze of computer when i have avast to scan ALL FILES (standard shield).SPybot will scan for a while but very slowly until system freezes.Only the mouse cursor moves around but nothing else functions (i.e keyboard or anything)and i have to do a hard reboot by keeping power button pressed in.It does not happen when avast is set to HIGH (standard shield).It is not a resource problem or cpu usage problem as i have visual monitors in system tray that allow me to monitor these things and gdi/system resources are in the 70s and cpu power used is as little as 10%.It seems that as spybot goes through its internal database of malware ,avast is also scanning them in the all files mode and seems to cause the proble,.Im using w98se.If this is not repeatable on a similar setup to mine then its obviuosly a config problem on my pc.One question i have is that ,does setting standard shield to high rather than custom and scanning all files make that much of a differnece security wise.
tia
me