We mostly do a Windows installation and re-installation. And there is few important thing before you re-Install windows that you MUST know and remember it. For some reason, a precious files could be lost by mistake and a mistake is a disaster.
What you should know and make sure that:
1- Backup your files
For a educational or teaching purpose,research and whatever it is that important to you,you never think about losing it, make sure you do a BACKUP. What is backup and how do you perform a backup. What i mean is you need to store or move to another local disk for example "Local Disk D:\" or "Local Disk E:\" or better backup in DVD/External drive.
2- Know Your nature of file
You use your computer and no one better than you to evaluate the files. So, Make sure you backup what you need and according to situation
3- My Documents
This is important thing and normally people make mistake about this. Default location for "My Documents" is in Local Disk C:\ and when you reinstall Windows and format the partition, all files will be gone. So, make sure you store and backup "My Documents" in safe place before do a Windows installation
If you "Crazy Surfer" and "Browsing Maniac", you should concern about this. Yes, people will not remember all location they bookmarks. If you do a format/Windows installation, the bookmarks will be empty and Firefox setting and configuration will be lost. Pay attention at this point.