Did you try to use different system restore points?
I have used system restore several times successfully, but sometimes it doesn't work.
You can re-install your downloaded student upgrade OS system. Clean Install with a Upgrade Windows 7 Version
If you don't have an ISO file then use the tutorial listed by rsvr85.
If you have an ISO file you can use one of these three methods. Windows 7 USB/DVD Download Tool Burn Disc Image - ISO or IMG file Install Windows 7 Without Using Any External Device
Backup is very important, you can save all your programs, user settings, personal files and data. If your OS becomes corrupted, non-functional, slow or infected by a virus, you can restore it to an earlier state with a backup in 15-20 minutes versus 4-6 hours to re-install, check drivers
, down load all the updates, install all the programs, find all your favorite websites, etc.
Then backup your OS and data partition every 1 or 2 weeks depending on how much you use it and the amount of personal data you accrue.
Your OS and personal data backups should be kept on a separate physical storage media, an external hard drive works well for this, in case your HD fails. They do fail.
The most recommended backup program is Acronis, at about $50 it will do the job very well.
There are several very good free programs that have been used for several years and are highly recommended. Macrium Reflect
Paragon Drive Backup can be found for free.
Hope this helps.