Your source files work fine on your friend's machine, so there's nothing wrong with them.
There is something wrong with your machine, and changing/reinstalling the software hasn't fixed it yet. Rather than trying an entire new Operating System [There be DRAGONS!!] I think you should work on getting your Windows 7 straight again. Windows 7 is a good, mature Operating System, and if a system develops a fault you should never hope to fix it by 'upgrading' your software.
If I remember correctly, NXT2 only allows you 10 installs before your key expires (it doesn't care about Repairs) so don't go uninstalling/reinstalling unnecessarily.
It would be useful for you to clean the machine up (logically) as Cdanteek suggested. This is worth the time it takes, and should be done regularly to keep the machine 'lean and clean.' The steps are Startup, Cleanup, Defrag, and Scan.
- First check the programs which run when Windows starts, and disable any that aren't absolutely necessary. Run MSCONFIG.EXE and uncheck unnecessary programs in the Startup tab. Reboot Windows, and it will start without those things running.
- Right-click on your hard drive in your File Explorer, and select Properties. Then click on Disk Cleanup, and in the box which appears, click Cleanup System Files. Windows will do some calculations, and when you give it the go-ahead will delete all the old garbage it indicates. I usually tick all the boxes and delete everything it allows. It's amazing how much there can be.
-Once you've done that, go back to Properties (first picture) again and click Tools. Then click on Defragment now, and go do something else while the hard drive is defragmented. It might take hours but it will be worth it, and it won't take so long next time.
-Now your system is lean and clean, you should make sure that this problem isn't caused by broken Windows files. Open a CMD window with Admin privileges, and type the command sfc /scannow <enter>. The system will scan its vital organs and replace any corrupted files. You might need your Windows 7 disc handy. Exit the CMD window when finished.
If you do all the above things your system should be running properly. Please ask if you have difficulty following my instructions.