yes I use 800 X 600 all the time myself
as for changing the size you have a program in your computer or you will have to download one its easy to do!!
Just go to your computer and right click on a picture and hit resize from the menue and chose the med size and you will be good to go!
If its not there you will have to download picture from power toys , go here and get the image resizer.
http://www.microsoft.com/windowsxp/d...powertoys.mspx