Basically your resources are being gobbled up by programs running in the background or / and in your system tray ( the part on the bottom right of your screen ) Antivirus software is a culprit of this.
You can look at whats running by clicking on CONTROL ALT DEL all at the same time.
If you want to turn things off you can access this my going to START ( Bottom left of your screen ) and then RUN...then type MSCONFIG. from there you will be able to access the start up procedure and you will need to click off the normal start up and click on the selective start up. After this the next tab will show you whats running at start up and you can decide what you wish to turn off. when you have unclicked all of the applications that you feel you do not want to run dont forget to click APPLY, before you exit.
If you are unsure which ones to unclick there are plenty of help pages in the helproom concerning MSCONFIG or do a search on click here and type START UP PROGRAMS and you will be able to find some kind person who has listed all of the programs you are likely to have. or try these... click here
However if you PC doesnt feel sluggish than dont worry too much about the resources figure, just use your PC as normal.