These are Microsoft Installer patch files.
If this is not a server, they should not be left around. That would be the reason to keep them all, so that you can perform a client install to lots of machines.
Unless an install failed, and they weren't cleared up, so they are leftovers....
Here is what I mean, explains the sort of thing they are and how/why they are used:
http://tinyurl.com/y4um7x
[b]"When you install Office on users' computers, Setup copies the installation files from the network to a local installation source on the client computer and completes the installation from there."[/b]
I wonder if this was the case, and such a network setup was done on this machine.
hmmmmmmmmmm
Not sure here, is it possible to back them all up somewhere, so they can be retrieved if needed, then try deleting them and wait for the sky to fall in?
maybe not....
Better to wait to see if some of my more knowledgable Network peers here in TR can suggest something, before doing that.
It's all those MSP files that are the space hog, they shouldn't really be there without a good reason for it.
That's all I can think of for now.....
Edited to add link and quoted extract