Your data files should be intact in your hard-drive (virus).
Here are some of my recommendation:
I'm going to assume that you have IDE HD set up from DELL. If you have another PC with IDE controller, then unplug the virus hard-drive from your old PC and then change the jumper in order to make it as a slave drive. (see the hard-drive for the jumper setting). During boot-up, go into the BIOS and make sure it recognizes your new slave drive. Once in Windows, then grab your files. Afterward, re-install the Windows OS. Since you have a DELL, they do provide a disk called "Operating System Already Installed On Your Computer" - Reinstallation CD.
IMPORTANT: try to backup the file
WPA.DBL in the Windows/system32 directory before you perform any re-installation. If you have this file, then it won't make you contact Microsoft to activate your Windows after the installation.
If you do not have an extra PC, then buy a cheap hard-drive for $30 and install a brand new Windows on it. And then follow the steps above. If you are in need for more disc space, then this is a perfect time to upgrade your hard-drive.
In the future, always make a copy of your important data onto another hard-drive.
Also, if you don't have access to Windows software, then you can always download the latest Windows 7 temporarily for you to get the data out... It's free until March 2010.
https://technet.microsoft.com/en-us/evalcenter/dd353205.aspx?ITPID=mscomsc
Good luck...