download ccleaner.it is a tool for clearing up junk files from your system. its free and its fantastic
the message is probably - 'your system is low on virtual memory'
virtual memory refers to hard disk sopace your system uses as virtual ram. according to the geek forums etal, it shoul be between 2 and three times your RAm.ie 512 mb ram - 1.5gb virtual memory and so on.
let us know your ram and the size of your hard drive. if you click on the 'my computer' icon and select 'propoerties' you will see your cpu, ram etc, based on this we can advise you on resizing your pagefile (thats the virtual memory thingy)
also, click on your 'c drive' and elect properties- you should see your hard drive and the free space on it.
as to formatting - thats for computer illiterates.
do you have your system drivers disc? do you have all the software on your system? the pc village scam goes something like this - pay for formatting, then pay for restoring your drivers, then pay for reinstalling your software. . basically you're paying for solving the problems the 'engineer' created. and God help you if he can't locate the drivers for your system.
you've backed up your files - guess what the virus could be in your files( if there is a virus) so restoring your files means you're restoring the virus. the IT guys in my company keep doing this- backing up and restoring viruses - (what do you exect from peeps that use mcafee

)