MSOCache folder

You found a folder called MSOCache with lots of files.
What is it, can I delete it?

Msocache is another of those directories that somehow just appears.
MSO stands for MicroSoft Office.
It's a local copy of Microsoft Office's installation source. Put another way, it's a copy of portions of the Microsoft Office installation CD. It's used so that you don't have to insert the CD when you add a feature, perform a repair operation, or install service packs and patches.
Msocache is created, quoting MS:
...if the following conditions are true:
One of the available hard drives has more than 1.5 gigabytes (GB) of free disk space available.
The hard disk with sufficient space is not a removable drive or a network drive.
Personally that seems kind of arbitrary, but there ya go.

You can delete the folder, but, that the MS Knowledgebase article says, "Never delete the MSOCACHE folder by using Microsoft Windows Explorer." Why, they don't say. They suggest using the Windows Disk Cleanup Wizard.