it could be any number of things... as already stated you could have more programs running in teh background than your system can handle..
virus? prob not. spyware? could be... as stated do a virus scan, i recommend AVG..
are there certain times when its slower or is it just always slow? IE: its only slow when brosing the com.
but to answer your question.... no, anti virues software has come a long way in the past few years and neally all including webroot wont be the cause of slowing a pc/lappy down.. lack my ram will but not av software..
also you might want to do a defrag ;)
Even if it takes up a lot of room, it's generally a good idea to keep your anti-virus software on your computer. If you get rid of programs you no longer need, clean up your files and registry, and defrag it'll help with your computer speed. Keeping your registry clean really helps keep your computer from being slow.
If your anti-virus program uses up a lot of system resources then yes, it could make your computer go slower. In general, though, anti-virus programs (unless it's a malicious program) should be okay to have.
Which anti-virus do you use?
you should scan ur computer.. when its done scanning it will tell u whats up with ur system.. it could be downloads.. usually limewire.. lol.. check it out :)
It might be a VIRUS...but I don't think that anti viruses slow down computers. I dunno for sure though D:
maybe to many programs running or its an old computer?