Its a crawl

Hello All:
My computer was slow this AM a bit and when I restarted the computer, it did a CHKDSK on its own. It wasn’t too bad afterwards but this PM it became a crawl. It takes 20 minutes to open a word file for example. The shortcut to an XL and another to a Word file could not find the files. To open the internet, again about 15 minutes.
About an hour ago, even though the key board was on lower case, when I tried to type this and post, it was printing all caps. I restarted the computer, hoping the slowness might get fixed, it didn’t. ( except it prints in lower case as it should).
Yesterday I changed my antivirus from Avira free version to Avast free fversion. But it slowed me down so I uninstalled it and reinstalled Avira. I shut down the computer after uninstalling the Avast. I have Webroot spysweepoer and had it for a number of years, so that is no9t new. I also have Superantispyware and Malware bytes. Tried to run spuerantispuyware and after 1 hour it was still scanning the registry items, some thing it flies thru.
The CPU usage has been max of 30% and as low as 1% per my task manager and the commit charge has been been above 800M and below 1000/5209MM. I had virus infection at my home computer and the cpu usage was 100% all the time. However, when I move a file on the desktop, the trail it leaves is just like the times when the memory is low.
Do you have any insight on how to fix this?
I really appreciate your input.
Thank you.
Webuser

 

Sorry, buyt I forgot to mention that my coputer is a DELL, core 2 quad, RAM 3.2GB, with MS windows professional SP3