Last night I installed Windows 7 for the second time, the first time I had the exact same problem and downloading drivers from dell that were 'Windows 7 compatible' didn't seem to fix anything..
Pretty sure from that picture you'll be able to see my problem and that's just a mild case of that happening, as you can imagine it is incredibly annoying while trying to play games or check my emails, hell just writing this is getting confusing. (Resizing the window seems to help.. for about 10 minutes.)
I never, ever had this problem with Vista. I'd really hate to have to go back to Vista again because of this.
I have 3GB of RAM and a Pentium(R) Dual core 2.0GHz processor.
32-bit Windows 7 Ultimate.
If there's any more information you need to diagnose the problem please let me know and I'll get it back to you ASAP.
I've noticed that it only seems to do so after doing something visually intensive like games and a 3D Chat application I use, after I close the application causing the problem it will not fix itself till I restart.
Unfortunately that's pretty much all I use my laptop for...