Hi all,
I am here for the first time as a desparate newbie in search of a solution to my problem and hoping someone can provide an answer. 
A few days ago, my PC suffered a power outage. Later when the power was back, I rebooted up and tried to continue my work, but found the system was responding in a start-go-start-go manner, as like you're caught up in a traffic jam. Took ages to get something done. I did a complete scan with my Norton Security 2009, but found no virus - the scan took almost an hour to complete as compared to the normal 15 min.
To cut the story short, eventually I found that if I were to kill the svchost that is taking up the biggest chunk of memory, the speed will come back to normal. Of course, the processes it runs will then start to activate all over again, depending on how they are set. I use a program call Process Explorer to do so, as I found it the most convenient to use. But I have to do this everytime I boot the system up, which is a real nuisance.
I shall be very grateful if someone can please tell me what is happening to my system. I am no techie, so you'll have to be patient with me. Thanks.
Ben
Edit: I forgot to mention my PC is running Windows XP.