CPU Usage suddenly goes high and harddisk light glows continiously..slowdown?Help

Strange problem,
I have pentium 2 about 400 Mhz and 140 Ram with windows 2000 Professional.
often suddenly the CPU shows high usage 80 to 90 percent and the harddisk light shows active for long time,..and when this is happening the PC gets very very slow ..well obviously,..
but i dont know why does the UPU usage suddenly goes high.
i checked in the Task Manager, and some times it is explorer.exe
which is using high percent of CPU....more i often see two "explorer.exe" processes open in the Task manager.....
i Tried to reinstall the windows but, it was ok for some hours and then again the same, .....Please Help.....Thanks in advance

 

Firstly, you might want to run a virus scan.
Explorer.exe is supposed to use a lot of you CPU, it needs to be there in order for Windows to run. And I suggest you get more RAM too, Windows 2000 needs a good bit of RAM to run, 256 megs would do it. But only thing I can think of is maybe a virus. Somethinf similar happened to me when I was running 98, and it turned out to be a virus. So try that, and look into getting more RAM, Crucial.com.

 

Thanks Lee for your Interest,
but i became so fedup with this problem, also i could see some unknown internetconnections active, even while the web page was already downloaded,...how ever, ...i cleaned the Harddisk ...and reinstalled the win2000, seems everything is working fine.
thanks....