Hmmmm, whom to ask..... here or elsewhere?

Greetings all...first post, so please forgive me if this is not the right place?
Scenario: old man..went from using XP pro on a couple of computers to a new computer with W7 ultimate... THEN I found out I wouldn't be able to run my old favorite programs (Dungeon Siege, Diablo and others) on my shiny new computer because of "compatibility issues.
Now, the big question I have is: am I stuck with this? Or is there someway I can change my shiny new toy so I can play my old favorite programs??
Thanks for any help or suggestions, even if it's bad news

Some companies are not supporting windows seven with hardware drivers or software updating, so bottom line is yes your stuck. Check with each of your games manufacturers for any possible updates/upgrades for windows 7 compatibility. You also might be able to play those games in compatibility mode in 7.

Try XP Mode. If that fails, you can maybe run XP in a virtual machine with VMware or VirtualBox. You can also look into a dual-boot scenario, although that's hardly what I'd call convenient.

I think he is asking if it's possible to downgrade to Windows XP. The answer to that would be MAYBE. The issue would be, are there drivers to use your new computer hardware in XP, and I can't really answer that - you might call the manufacturer though I doubt they would be of much help. We are lucky when a company provides drivers for new OS's, I doubt they have even tested old ones on their new hardware.

You probably have a better chance of using XP mode as previously suggested. XP mode is a free download from Microsoft.com if you have W7 Professional or higher, other Virtual PC programs are available if you have premium or if you simply prefer them to Microsoft but you will need your own license for the OS you install if you don't use Microsofts' option.

Yes,
Windows 7 is much different than XP.
Since you are running PRO or higher (you say Ultimate) then run your games in XP mode.
I had the same issue with Warcraft III, another blizzard game as you mentioned.
see: www.blizzard.com for official and recommended solutions to getting their games to function properly under Win7.
To run any game (or any application) in WinXP mode, right click on it's icon, whereever its located, and in the menu that comes up, click compatibility.
Follow the screens.
FYI, the new releases from blizzard, up and coming, are fully compatible with Win7.
Hope this helps.
Mike.

mike3's suggestion would also be my first, and simpler try.
But you right click the .exe. Select properties. Click the "Compatibility " tab.

Click the small square and select XP(Service Pack 3)
Click the small square, at the bottom of the window "Run the program as an Administrator"
"Apply"

It's certainly worth a shot?

Yes, I concur, if you haven't tried compatibility mode that is definitely your first try.