In order to install a script on a hosting package if the domain name does not point to it you need to edit the file:
C:\Windows\System32\drivers\etc\hosts
and add the domain name and the IP of the hosting package like this:
XXX.XXX.XXX.XXX
www.your-domain.ext
Replace the X with your domain IP
To open the hosts file On Windows Xp you can doit trough notepad. Simply open notepad and click on File -> Open then browse to the desired file and click OK.
To edit the Hosts File on Vista you have to Open Notepad with Administrative privileges by clicking Start, All Programs, Accessories, and then right-click Notepad and select to open as Administrator. Now that Notepad is open with Administrative privileges browse to (C:\Windows\System32\drivers\etc) in Notepad and open the hosts file.
If you open the hosts file on Windows Vista and then attempt to save it as a regular user, you will get an error message as show in the screenshot below ("Cannot create the c:\windows\system32\drivers\etc\hosts file. Make sure that the path and file name are correct):
The reason for the error message is not that it cannot be created, but that you do not have sufficient permissions to write to that file.
Running notepad as administrator
The solution to this error is to run notepad (or other editor) as administrator and you will then be able to save the hosts file with no issues. To do this, locate the "Notepad" program on the start menu (it's under "All Programs" then the "Accessories" folder. Right click the "Notepad" icon and select the "Run as administrator option as shown in the screenshot below.
By this your computer will resolve the domain name to the hosting package that you want and it works just like when the domain name points to that server.