You got some REALLY bad advice on this.This is NOT a conflict between Generations Family Tree Plus and XP - I'm running the software on my system with XP at this moment.
What you are encountering is a conflict between Generations and some other program or driver on your machine.Please take a look at the Generations Tip on program interactions.The Generations Tips are available on my website at http://users.sisna.com/mhobarthttp://users.sisna.com/mhobart and also in the Generations Tips folder on the Sierra Genealogy Q&A message board http://www.sierra.comhttp://www.sierra.com [follow the message board links].
I have given genealogy.com permission to use the tips in their prepared answers in the support/query area for Generations Family Tree/Plus.
I am concerned that they did not check these since you say that your dialog has been going on for months.
The most common culprits for this syndrome are the helper programs for some of the automation in Omnipage (not the main parts of that program), certain popup stoppers, certain fancy mouse drivers, and the tray icon display options program for selected nVidia graphics cards.
Let me know if you still cannot isolate the culprit after you have reviewed that Generations Tip.