Active problem installing antivirus software.

[Active] problem installing antivirus software.

hello well i am facing few problems but i dont know if its all related or not so have explained it in detail below.

1.) i am facing this problem of difficulty in installing the antivirus software since 1 wk. well i have avg software but it didnt get updated many times coz of error msg "invalid binary file ". so thought would unistall and reinstall. butt installation failed many times. so thought for the time being would use 30 day trial pack of bitdefender or kaspersky both again are not getting installed. says installer termeinated prematurely.

finally did install avg and updated it when it detected a virus which it healed.

but other antivirus are'nt still able to install.

i have other problems too.
2.) wen was working on picasa repeatedly it kept on updating thunbnails of a folder which is already fully update.

3.) repeatedly i recieve msg as to low virtual memory. paging file size is initial size 322 to max size of 744

4.) i have all my songs in D drive. suddenly all mp3 files are showing as jpeg image files. and are not opening in picture viewer or real player or windows medis player but opens in vlc. this is 2nd time it happened and i deleted all files and put them back using backup cd.