...I will give you a few links...to see if we can get your icons back...But change the location of your icons to the proper folder first.

And yes another app may be messing with them. Another thought is that you may have a virus, trojan etc.
Pc Inspector this is free...
This is a link to a post here listing programs ...I would suggest for now A-squared ..Of course get any others that you don't have if you choose
Utilities for WindowsNote I am not sure if these work in Vista
I suggest trying to find your icons...scanning your system with Anti virus & the other programs
Post back & let us know if anything helped.
Since the icons disappear I suggest Drive Sentry.(free 30 day trial)..also in that post I linked to...the reason is that this program will ask you if you want to allow permission to access files...you will need to read instructions throughly....and select...trust this program then allow & remember in the popup to let normal programs through. This may help you find that program that is hijacking your icons

It can be annoying while it gets used to your trusted programs...but boy oh boy nothing will get through that shouldn't.

once you have gone through teaching it. It will use about 50% resources initially while it is scanning your system...but then uses only about 1 %
Please Post back & let us know if any of this helped
It's My Secret