If you have your restore cds that your pc came with, try formatting your pc and reload the OS and then install the latest DM. It sounds like you may have a registrey issue. Easiest fix is to just dump the pc and start fresh. I'm a bit of a pc fanatic (as with BB too) and I tend to format and redo my pc OS about every six months or so....
Posted from my CrackBerry at wapforums.crackberry.com