I am running the game on windows vista 64. It installed no problem with both disks and I installed it as an administrator. I set up a Live account. I am not getting the que's for any of the DLC add-ons. I have been out of the vault for quite some time. I checked the data directory and their are files in there with the DLC names. What am I doing wrong?

Thanks

Start the game through the Fallout Launcher, click on Data Files, then check the boxes beside each DLC (ThePitt.esm, Zeta.esm, etc).

I have the same issue, the check boxes does not stay checked, however all the mods works both the dlc and user mods.
If the dlc is loaded you should get a lots of new quests, once out of the vault. Think broken steel is the only one who don't start a new quest from the start.