- Uninstall 7zip if you think that could be more than a coincidence
- Try drive in another system if possible
- Try a different IDE cable, preferably one that you know works
- Switch IDE channels and position (master/slave) for HDD and Optical Drive
- Double check jumpers on optical drive... play with those settings as well.
- Try another drive if possible to see if it's a problem on your IDE channel.
- If its a new install of the OS, try reinstalling it and see if it gets detected (this is a bit of a nuisance, but if you have the time, and you haven't done much with the system yet, its worth a shot... otherwise I probably wouldn't bother)
After doing that, you can be sure whether it is the drive that is at fault, or the system. Those tests should only take a few mins. Keep the case off, change one thing at a time, boot up.... rinse and repeat until you can draw some concrete conclusions.