Advantages

You may not loose any data or your preferences and be able to recover your data and/or operating system.

Disadvantages

Only works in about 50% of occasions and any Hard Drive problems are not detected, viruses remain. The success rate can differ from operating system to operating system. Unfortunately you may find that problems get worse or different problems arise from trying this method.

Windows NT, 2000, and XP repair option can cause problems due to different service packs being installed, to what is available on the Windows Disk.

Windows 7 and Vista only has repair option for startup problems.

Due to the original disks not having update downloads you may find Windows very unstable until you download and install the service packs and updates that had been previously been on your system.

 

How to do it

Windows ME, 98, 95

You start the windows installation and reinstall in same directory.

Windows NT, 2000, & XP

Use repair option during install.

Windows Vista & 7

System restore, restore backup, startup repair and memory diagnostics are only options available from vista and 7 dvd.

Windows Vista

Try upgrading Vista to the same version using the upgrade option during install. Its an unofficial way of doing this.

 

Extra Notes

Windows 7, Vista, NT, 2000 and XP users have a distinct possibility of loosing all their personal data if they set the login name the same as the previous install.

Windows 7, Vista cannot be parallel installed onto the same partition as any other operating system.

Due to the original disks not having update downloads you may find Windows very unstable until you download and install the service packs and updates that had been previously been on your system.