The thing about collecting vintage computers is that unlike any other item, except maybe guitars (as there are millions of knock off Gibson Les Paul and Fender Stratocaster copies made every year by various names, but they are at least done by a couple "ghostbuilders"), there are TONS, I mean TONS of no-name knock-off "clones" out there from the 8088 based XT's on forward. It's a tough call weather to make such "generic" devices collectable or not, since it's hard to gather all the manufacturers over the years.
You have your major Manufacturers: Compaq, IBM, Dell, Gateway 2000, Epson, Tandy, and so on, but for every one of them you got a whole pile of white box Manufactuerers like: GEM, Flight, Cactus Computers ID., AMT, CSI, a million Everex, Kingspao, MSI, In-Win, SongCheer, ASUS, and other chassis all labeled with a myriad of names, some don't even have nametags as they were built by their original owners (and sometimes second and third hand too). You also have "ghostbuilder" stuff too, like take for instance, I had an IBM PS/Valuepoint computer awhile back, that one, instead of IBM PS/Valuepoint on the front, it had GTSI Desktop Computer on the badge. I also recall some kind of custom made Compaq 386 system made in the late 80's for some special purpose that went under a different manufacturing name (Compaq was the "Ghostbuilder").
The thing I think a lot of people forget is to separate the Vintage from Collectable. Vintage is an age Vint-AGE, collectable is weather it's actually worth anything or not. I consider most computers 15 years old or older vintage, which includes pretty much anything 486/100 on down. Once it can happily run Windows 2000 or XP, it's pretty much moot to collect it, since a modern machine can do it.
Now the real collectable stuff in the x86 category, original IBM PC 5150's, 5160 XT's, 5170 AT's, Compaq Deskpro 8086/286/386 (preLPX, they did not make many of those early computers as they were Top of the line when they came out), the original Compaq Portables pre-laptop, the original foldable Laptop jobs by Zenith Data Systems sometime between 1986-1988, weird oldies like the Amdek 286/a (which was manufactured by Wyse, and used a backplane/daughtercard design, and a standard Wyse terminal keyboard).
On top of it, you have some really weird clones, like the GEM computers I have are pretty strange (one of em' has a Deskpro style case that I have not seen ANY other manufacturer use), you have some XT clones that have the Car-Hood-Like "flip-top" cases, rare IBM Blue Lightning motherboards in some early 90's systems. There's so much out there just in X86 it's hard to list it all and make a definite answer on it, unlike, say, things such as the COmmodore 64 and ATari 400/800, which were in their own design league with their or archetecture. Macintosh is 1000X easier to classify and estimate value on than an old IBM Compatible, because the variables in collecting IBM compatibles is practically through the roof, and subject to TONS of sub-classifications (portables, XT desktops, Semi-Compatibles, AT Desktops, Clones, Originals, Rarities.....yadda yadda).
In the end though, vintage to me is just whatever the mainstream is not using, I even consider some Pentium I machines vintage now, because you don't see people with a Pentium 60 very often anymore, most of those machines were junked at least 4 years ago.
