CPU fan or PSU fan are the other two things that would "groan".
Burnt smell might be the bearing in the fan. Works fine while cool, and then dies when hot.
The version of shopvac on the website doesn't work right. Something gets totally screwed up in the code when it's uploaded, and there seems to be no fix (in over 2 years).
Get the one that works, including the undo.bat that will reverse any damage done by shopvac.
http://members.cnx.net/reboot/shopvac.htm