Sega

Yep Heavy Gear is Activision.
I think it's possible to re-release licensed games or you wouldn't have games such as Judge Dredd being re-released so many times but I think it depends on the IP. You still need permission, I believe, from the ones holding the IP. If they feel re-releasing an old game might damage their IP, they may well say no. Ironically, the Judge Dredd games are all rather crap yet MechWarrior games are generally ace.

Judge Dredd, along with the rest of 2000AD is owned in full by Rebellion.

Any, and all, Infocom games (both text and graphic).

Wow no wonder. Ignore what I said then :P.

Are both earthsieges and Starsiege part of activision after sierra was bought out, would be a good alternative if mechwarrior never made it out.

Well, if Mechwarrior 2 has a snow balls chance in hell to be released. Then it looks like I'm going to have to find an old P133 or PII with a 3dfx card to play it with. Luckily I still have my old Midi plug style joystick hanging around.
Legal stuff sucks sometimes. Especially something this old(as-in computer years old). It shouldn't be a huge issue. But it sadly is however.

XP isn't the problem here. Vista/Win7 is, which I've been using on my flagship desktop ever since I first built it two years ago. Small price to pay to have an OS that won't slowly break down and refuse to boot entirely in a year each time it's installed.
I don't run XP as the main OS on any of the computers I own save for a secondary desktop computer in storage that runs XP ONLY for game compatibility reasons.
However, it's also perfectly possible that modern DX10-or-greater graphics cards like the 8800 GT could've played a role in MW2 not working.
As for MechWarrior 2 3D API support, it depends on which version you're running. 31st Century Combat had a common software-rendered version and a whole crapload of 3D-accelerated versions bundled with graphics cards and tailored toward that card's proprietary API (remember, this was before Direct3D and OpenGL were common in PC games). One of those was indeed 3dfx Glide (a very early version that only runs on Voodoo1 and Voodoo2 hardware). Ghost Bear's Legacy is only software-rendered unless you have the Titanium version. Mercenaries supported Direct3D, but not Glide or OpenGL. Titanium may be different, but I don't own it.
You're talking about Battlezone 1, though. Only played demos of it, but I'd buy Battlezone Gold in a heartbeat if GOG sold it.