I need a antivirus software but i cant afford one is there anything i can do ?

AVG is free

http://www.filehippo.com

I need a antivirus software but i cant afford one is there anything i can do ?norton 360

go to AVG, they have one for free. http://free.grisoft.com/doc/1

I need a antivirus software but i cant afford one is there anything i can do ?photoshop

Be aware of what you are doing, where you are going, what you download and run on your PC. Anti virus software is a backup to having a brain. Or for those that choose not to use their and simply rely on a program. There are several freebies out there. Check out www.download.com and see. You can also use free online tests from some of the major AV makers.
Housecall.com has a free virus scan
Google Pack has a free antivirus program.

Go to google and check it out.
You have two great free options

Avast:

http://www.avast.com/

And AVG

http://www.grisoft.com/doc/1

Both are good, and will provide you with the protection your computer needs.
There are two I know about, AVG and AVAST, both with free updates, I use AVG.
For PCs, use AVG antivirus. You have to click through their web site a bit to find the free version, but it's there...

For macintoshes, you also have ClamXav. (Not that there's much of a virus problem there...)