Computer slowdown, worms/trojans?

Jake'sGran

From time to time my computer suddenly becomes very slow indeed. I always check the security (McAfee) which lists what has been happening and that the firewall has prevented entry. And then I usually do a System Restore which seems to fix it. Does this happen to other people? If so, how do you deal with it.
NB I also get rid of the cache.

swift_gti

Next time your pc becomes slow bring up the task manager (right click the windows task bar and select Task Manager) then go to the processes tab and sort the items by the 'CPU' column (click the column heading to sort)
You are looking for the item using the most CPU time, note down the details of the first few items and post back with your results.