Graphics: ASUS VS247 (1920x1080@60Hz) 64MB GeForce 6150 LE (Dell)
>>>>>> you posted...
You have only 64mb of video ram for your video port. It's NOT going to work well covering 1080p and 24in. monitor as you already saw. You need at least 512mb or better, like 1gb of video ram(on video card). Take that info and find the cost you can bare. Robert offered the ATI 5450, but the 5550 maybe slightly more in cost but better. You could find one with 2Gb of ram and that's even better, plus both have HDMI port, what a match. The beauty of these cards is they will generally be supported by the current PSU, so you don't have to upgrade it. BUT!!! if you get some super-duper hot video card, then a better PSU should be part of the upgrade as well for long lasting operation.
When you get the new video card, clean out the dust bunnies while you have the PC case open to help overall.