Have you reinstalled your Graphics drivers, it sounds like you are viewing the screen in a large resolution (probably 800x600). Windows will probably let you adjust it to 1024x768 with the default drivers but you need to install the proper ones for your VGA device.
Right click a blank area of the desktop,
select Properties,
go to the Settings Tab and see if you can move the slider to the right to get a better screen resolution. Accept the changes when asked if you like the new size.
Then check the lower right corner of that window in the Advanced tab,
go to the Adapter tab and look at the Adapter type and Name information,
if it shown as not available you have not installed the correct drivers,
often a Windows Update will be able to find the right driver for you if you don't know which one you have.