Type "demoui" in console and load the demo you want. You can also summon that window by holding "SHIFT + F2".
From what I remember there's also a thing demoui2 or something like that, but I'm not sure.
Alternatively you can just type in console play "demoname" or it was playdemo or viewdemo or sth [can't really remember sry ;d]. Probably you'll also want to manipulate the demo [stopping; fastforwarding ; etc.], so demoui is more recommended ;)
If I remember correctly... I deleted all Portal files and pasted into that folder Source Unpack. Voilà :) [Yes these aren't "some files" like I said before but actually all files] (but this way it works like I wanted ;) ) And if you want to use LiveSplit you can type "-novid -window -noborder -w 1920 -h 1080 -x 0 -y 0" into Portal startup options (in Steam). Hope it helps :)
Yes! I did it! :D I swapped some files and now when I click "play" Portal button in steam library, it startup the 5135 source version of Portal :))))
Where do I save the vault.dem file? I know that the vault.sav in SAVE folder, but where vault.dem?
"Shift+F2"- it open (and close) demo playback. Then simply click "load" and find demo you want from files. With demo playback you can also control the demo (pause; resume; rewind; etc.) I hope I helped :)
Shortcut to what exacly? Cuz shortcut to portal.bat (portal.cmd) don't work if you have that on mind.
It don't work this way, because to add it to steam library as non steam game it has to be an application ('.exe'). The source unpacked version of Portal is started up by '.bat' file (for you it's probably '.cmd' ['.bat' is on my computer]). I was mixing in steam game files to get what I want, but I can't find it out. However Portal is strange to startup without steam and any shortcuts (to startup from files). In other steam games, for example Portal 2, you can go to game files and just startup Portal2.exe. In Portal (1) game files there aren't any Portal.exe file or something like that ;/
So I have a question: Can you make steam startup the source unpacked version of Portal? I mean when you press "play" button in your library.