Lets imagine that for the past few years software has been deployed using Group Policy Software Installation and that a single server has been used to store the MSIs.
The only issue is you now want to move the MSIs to another server or even better are looking to move the MSIs to a DFS share.
The ovious option would be to remove and reassign the software packages pointing them at the new path; the issue here is that the software would then go and reinstall its self on all of your PCs!
A better option is to use ADSI edit to change the paths that already exist without having to reassign the software. The procedure in the screen shot sequence below uses the instructions found at this Microsoft KB – http://support.microsoft.com/kb/2395088.