Vista has hidden the files in a user related location on the hard drive. You can fix this by re-installing Aces High II, right-clicking on the AH2113.EXE file and selecting the "Run as Administrator" option.
Then you will need to so the same thing everytime you want to run Aces High II in order to keep the files in the standard locations.
Basically, you are not the administrator for your computer anymore. Whoever installed Vista for you is the administrator. Vista has this new feature called UAC (User Access Control) which does all this. It can be turned off, but only immedaitely after the OS installation or else things go South for the winter very quickly.