I was able to run the demo of Monkey Island 1 on my PC...

[Fleshstalker]

Using XP and it was working well. The next day, the demo won't run at all. How is this possible. I heard XP is not suppose to run old Moneky Island games, but mine did and then the next time I booted it up, it would not work no matter how many time I tried. Oh and I don't even have the SCUMM download to make older titles run on XP.

[Steel Drummer]

Download SCUMMVM. That's the only solution I can think of, since I don't own XP.

[Fleshstalker]

Yea, I know it would work if I downloaded SCUMMVM, but I just find it strange how it worked the first time and then it didn't the next day. I find it strange.

[Mr Flibble]

Share and enjoy.

Downloads page

You're right, it is rather strange. Have you updated or changed anything at all, or possibly a program is running that wasn't before? Maybe a program isn't running that was before?

[Fleshstalker]

Nope. I haven't changed or update anything on my PC and nothing was running while playing it the first time or afterwards. Oh well...

[Magic]

PCs are so utterly complicated that a simple answer is sometimes not possible. I can't believe the amount of problems that I've solved with a reboot without making changes, nor the few times that a program hasn't run and then has run without problems the next time. 

They are fickle beasts, in short. Understand as much as you can but know that you won't understand them all.