I want to uninstall the antivirus which is presently installed in my computer.but when I am trying to delete or uninstall it it shown that it is write protected or disk is full.also I can't install any other anti virus s/w.
What can I do?
Please help me.

Publisher, title and version number of the anti virus software?

Which operating system (include version and service pack if applicable)?

Are you attempting to remove the anti-virus while logged in on an administrative user account?

How much space is available on your hard drive? If it's a small amount can your system utilize a drive with higher capacity? Do you have installation media to reinstall the operating system on a new drive?

As you didn't mention which anti-virus program you are trying to remove, try starting Windows in Safe Mode, then remove the program from there using the Control Panel, Add/Remove Programs.

Try to delete all the junk files and temp files (temp, %temp%, prefetch).
Try to uninstall the software again and follow these steps for norton anti virus as same for any other anti virus.