|Explain what you need to do. |
Are the computers currently running WinXP?
Is the intent to upgrade to a newer version of Windows?
The very first thing you wll need to do is determine if any or all of the computers can run WinXP or Windows 7.
If they are currently running some version of Windows older than WinXP then you most likely can't install Windows 7 at all.
In addition to the above minimum requirements you need to be sure hardware drivers are available for the version of Windows you want to install.
Finally, the fact that you are asking this question indicates to me that you may not have the knowledge to perform the task in 1.3 hrs, if at all.