I'd avoid the upgrade altogether and go for a completely clean install. Any problems or issues your PC had before the upgrade will more than likely be there after it. What i'm thinking happened is that when you upgraded from Vista, there were specific drivers for certain hardware items made for Vista and now that 7 is in place, it doesn't like the Vista Drivers. One thing you may want to try is uninstalling any and all drivers for all your hardware such as Video, Audio, Printer, Digital Camera, Webcam, Scanner, and other items. After you uninstall all drivers, unplug any extra hardware or USB cables except for the mouse and keyboard.
Download C Cleaner from here:
http://www.ccleaner.com/
When you run Ccleaner, you'll notice different cleaners you can use on the left. Use the top 2 only. Run the first one which is the recular cleaner. Analyze on the bottom left and when it's done analyzing, then clcik the clean on the bottom right.
When that's done, change the cleaner to Registry, and then analyze. What this will do is find all the leftover and unused extentions and crap from your registry. Things you've already deleted and uninstalled, but they left footprints in the registry. When it's done scanning, click the botton in the lower right to get rid of all the shit. You don't need to create a backup either.
Then restart the PC. When Win 7 boots up, it will see the audio and video and install it's own drivers. When it's fully up and running, go do a Windows Update and look for anything extra.
Then find each piece of hardware you have like the Printer and whatever else and go to that manufacturers website and download the drivers for that specific model and save them to the desktop. Make sure that you get the specified drivers for either 32 bit or 64 bit Win 7 depending on what you have. If neither is there, try the XP drivers first. If you have Windows 7 64 Bit, then try the Vista 64 bit drivers.
Plug each hardware item back into the PC. Windows will see it and ask what to do. Just click out of everything and when that's all done, install the correct drivers for that piece of hardware.
Good Luck
If this doesn't work to solve the problem, then you may need to do a complete reinstall from a clean drive.