screen size i effed it up

now its set to 800x600 i forgot what it was set to befor, but i went to display and moved the slider to the right one notch, i cant get the screen size back to where it was befor. How do i do it? What led up to this was i was installing my printer an HP 1315, befor it tried to install, it found and ok'ed the OS,CPU,RAM, free disk space, but the last thing the screen resolution was too low, so thats why i changed it but now things are way too small, but to top it off befor i adjusted anything the screen seemed fine to me.. oh and incase it helps the comp is a dell demiesion 2300, windows xp os

Click on:

Start
control panel
Appearance and themes
Display
Settings
then move the screen resolution slider till you find the one you like. You can then go into Advanced settings and change the DPI setting if you need to.

Thanks, although there were no more settings to go back, since as you move the slider to the right the screen images get smaller, and although i only slid it one notch, it reset itself, and there is no notch to go back, so i just did a restore to yesterday and its fine. with the exception of i can not install my printer again since it says the resolution is too low..Thanks again for your help