This antivirus method is virtually totally free..and legal.

1.Download this
http://www.kaspersky.com/kis_previous_versions?downlink=206909454
2. Install and activate 30 day trial version using internet
3. Download its updates separately at
http://www.kaspersky.com/avupdates/zip?open=av-i386-cumul.zip#open
4. Apply updates to kis7
5 When ur trial version expire:
a. then uninstall kis
b. Search on google ccleaner exe
c. download and install it
d. Clean ur registry using ccleaner
e. again install kis7
f. first apply previous updates and then update direcctly
g. restart pc whenever prompted