How to scan your PC with reliable online antivirus?

If you do not have any valid anti virus on your PC and you want to make sure your are safe then you can visit following sites.
Among them are

1. Eset : http://www.eset.com/online-scanner works only with Internet Explorer
2. Avast :http://onlinescan.avast.com, and
3. TrendMicro :http://housecall.trendmicro.com

All of these allow you to initiate a system scan without installing a anti virus software on your PC.

Pros:

1. Its free.
2. Its updated with latest virus database.
3. No disk space.

Cons:

1. Slows your internet connection
2. Slows you PC upto certain extent.