GRUB screen after cleaning

I had to replace the CPU cooling fan mount and decided to clean up the inside of my pc with a vacuum. Now it boots to display "GRUB _" instead of Windows 7 and goes no further. I played with the boot sequence and was able to launch W7 once, but it took nearly an hour to fully boot. I also removed the HD and checked it in another machine, cleared the CMOS x2, and check all connections x2.

I'm worried that I broke something. But from what I can gather about GRUB, this has something to do with duo boot and Linux or Ubuntu. I've never had either OS, so I'm really confused. Any advice is greatly appreciated.

I unplugged my KVM and USB hub, but no change. Thanks for the reply, though. That gives me some assurance that I didn't damage anything. I'll keep working on the assumption that this is the issue.