Hello slrohlik and welcome to Seven Forums.
MSP files are package files created when Microsoft products (operating system, Office, etc) install updates, patches, hotfixes, etc. These files usually appear in the Installer folder, and sometimes they aren't automatically deleted after the update is complete. Some MSP files can be deleted without creating a problem; however, others can cause data loss. Before deleting any of these files I would suggest you create a new restore point. Better yet, a system image using either the built-in Windows 7 imaging tool or the free Macrium. System Restore Point - Create Backup Complete Computer - Create an Image Backup Imaging with free Macrium
A technique that may help prevent deleting a critical MSP file:
1. Open your Windows Installer folder. You should be able to do this by clicking the start button, type installer folder
in the start menu search box, and open the folder(s) that appear in the upper panel.
2. Make note of all the files in the folder(s) that end in MSP. To simplify things you could copy/paste the file names into Notepad or a Word document.
3. Open Registry Editor. In the start menu search box type regedit
and click Enter.
4. Click "My Computer" in the registry editor (left panel) to highlight it.
5. Click "Find
" in the "Edit" menu.
6. Type one of the MSP file names into the search box.
7. Take note of what happens after you type in the MSP file name. If you get the message, "finished searching through the registry," you can safely delete that MSP file. But if registry editor is able to locate the file and places it in the "Data" column, then the file should NOT
be deleted. Doing so may corrupt your Microsoft data.
8. Repeat Steps 6 and 7 for each file.