Massive PC file name conversion?

[SzczerbiakManiac]

I have about 1500 files and I need to make two tweaks to all of them:

1. Convert all underscores to spaces
2. Delete the last five characters, not including the extension

E.g., If a file was named "Image_File_Name_2012.jpg" I want the new name to be "Image File Name.jpg". I don't mind making two passes, one for each action, but I do NOT want to manually edit each file.

Is there a way I can automate this process?

ETA: I'm running Windows 7