The power of advertising!
People (including my own parents!) pay for stuff like QuickHeal when there are perfectly good free alternatives such as Microsoft Security Essentials and AVG out there. Mainly because QuickHeal advertises a lot. Wish they’d asked me (maybe).
Anyways:
You can download “Microsoft Security Essentials” from here: http://www.microsoft.com/security_essentials/
And AVG Free (Personal use only) from here:
http://free.avg.com/ww-en/download-avg-anti-virus-free
Both are excellent. You should have one of the two installed at all times! Both have been installed on millions of machines and are relatively stable, known to be solid (not crashy) and won’t slow your computer down too much.