i have a computer running windows xp and have some sort of hijacker virus on it,
(I open internet explorer and the homepage changes after a few clicks, redirects, and if i try to open my yahoo inbox it redirects me again to a red screen that say my computer is infected, I installed msn explorer to try and get my yahoo mail and it works in that browser but if I go to ie it comes back)
i downloaded the avast virus cleaner but cannot open the file or any antivirus or firewall for that matter
help 
Hi Bandit
This is Spyware/Adware not a virus.
I suggest downloading, updating then running these 2 good free programs, they are ad-ware
and spybot.
Also after that could you post a hijackthis log here so we can check your system is clean.
You can get hijackthis from here and this is how to use it (incase your not sure how)
i downloaded the avast virus cleaner but cannot open the file or any antivirus or firewall for that matter help
Did you try re-downloading it?, do you get any errors while trying to open it?, have you tryed any online virus scanners to check your system for viruses?
–lee