Reinstallation of system?

I got a virus yesterday, my whole computer has gone mental.

Its really slow, takes ages to load up, most applications don't work. It deleted my virus protection, and won't allow me to install new things. Internet explorers never load.

I'm trying to back up onto ipods, cds but it won't let me copy files across.

I NEED TO DO MY COURSEWORK over the half term.

I was wondering how I could do a system reinstall so that my whole computer would be as new again. Is this even possible?

Thankyou for any help, I really appreciate any ideas you have.

Reinstallation of system?norton antivirus 2007

The best thing to do is a system restore by following these steps:

Go to Start - All Programs - Accessories - System Tools - System Restore

Ensure the 'Restore my computer to an earlier time' option is selected and click next.

On the calender find the day that you installed the software (the days with available restore times are highlighted bold, if you click the day you will get a break down of what software was installed/un-installed on that day)

Select the appropiate day and click next

Complete the wizard by following the on screen instructions.

If that doesnt work try doing this...

Press the windows key + R (this will open the run command, if this doesnt go to Start - Run)