GirlWithAProblem:
Hmm ... I wonder if your video/graphics card is dying? What type of CPU have you, if you know? (Likely an Intel, I'd guess.)
I'm wondering if something is overheating - CPU? or the video card ... ? The card must be seated properly, otherwise you likely would not enjoy that hour.
How much memory (RAM) have you in the HP? This could be a memory problem, and by rebooting the memory gets flushed ... and the problem is (temporarily) resolved ... ?
What percent of System Resources do you have when you first start the computer (Rt-Click MyComputer, Properties: should see "System Resources") vs percentage of Resources when images no longer display?
When did this problem first appear? What did you do, if anything, to your computer (e.g., add programs or hardware) prior to this problem rearing its ugly head?
Brangwen