The command regsvr32 registers DLLs in the registry. In this case its the Java and Visual Basic script dlls. The fact that you received no error messages when you ran the commands suggests that they ran OK and they cured the problem.
So either something is removing the entries from the registry on bootup, perhaps a virus, or the registry is corrupt.
The first thing to do is to run a full virus scan then try running CCleaner, click on the registry icon and place a tick in the "Applications" box then click the scan for issues and see if it flags any entries relating to Media Player.
Hope this helps.