Regedit
Go to edit and click find
Type in MaxResolution
Click on Find Next
Should display and highlight the MaxResolution line which will have a value in the format of "1600,1200" or in your case "1024,768"
To alter right click on MaxResolution and click Modify, type in your desired MaxResolution, i suggest putting in 1600,1200 and closing regedit.
At this point nothing will have changed other than the options up to 1600,1200 will now be listed under display settings.
From here its up to you to select a higher setting and experiment to see if your monitor really can display it.
Remember if you cannot see the screen and it corrupts up at higher res, windows will change back down to last working resolution after 15 seconds.
However if it overdrives your monitor and fails to display anything but garbled rubbish it could potentially damage your monitor, so i would suggest if this is the case either hit escape to force a switch back to lower res or power off the monitor wait 30 seconds to be sure and power it back up.
All of the above will be done at your own discretion of course as registry editing can be a dangerous pursuit , or so they tell me.
The route in registry for me is
HKey_Local_Machine
Enum
Monitor
000