Hey just noticed your in Lowell, I'll be in Woburn and Salem Friday.
Vista is a weird animal. Its recommended that you DO NOT install the game in the "default" location because vista moves crap around on you. So if you installed it in the default location the hirez file may or may not be in the right spot.
If you have installed the game in a location C:\Games\Aces High, then navigate there, and click into the cashe folder then into one of the plane folders, if you have a 1024 TCA file as well as the 512 then it is installed.
The 250 should be good enough for you to have the bells and whistles, IF its installed right. Make sure by running the Dxdiag and see what the computer is running.
Thats all I have right now, good luck!