GSAK will not do this.
I never used Geocache Manager. See if you can export from it in another format.
Magellan offers the free program Vantage Point that works well for eXplorists, and works in Windows Vista.
Tried Vantage Point and currently have it installed on my Vista laptop, but it doesn't import the .geo files that their old program created. I was hoping that it would just import that file but it only would allow me to import .gpx or .loc files.
Unfortunately there is no other option to save the files as on the Geocahe Manager program.
Magellan support has also been non-existent when I sent them an email on this issue. I greatly appreciate your help and ideas!