Did you try a different monitor? It may be the monitor that is manifesting the lines.
Did you do a clean install of the driver like I laid out for you?
Is this win7 64 bit you are playing with? If so, here are the drivers for it...for your machine:
http://h10025.www1.hp.com/ewfrf/wc/soft ... 72323#N211HP modifies the drivers to run in their machines and that may be your problem...you aren't using their driver for graphics, chipset and such.
Shut off the anti-virus!
Use the control panel to uninstall the driver and say no to the restart.
Find the video card folder and delete it, then empty the recycle bin.
Get CCleaner, install and run the registry section of the software to clean out the bits and pieces left over.
http://www.filehippo.com/download_ccleaner/Restart the pc.
say no to the popups.
Shut off the anti-virus!
Install the new driver you got from the HP site and reboot as instructed.
Is the line still there?
Nasty
Nasty