This question arose one day, and while it talks mainly about Quicktime and MPEG and mp3 formats, a lot of the general information here could be applied to any situation concerning creators and types on Macs, and File Association issues on PC's.

“Speaking of changing stuff on PC's, how do you change file type/creator info on a PC?

“The classic example is MP3's in Quicktime format - if a PC user downloads them and they were made on a Mac, then the file type is MPEG/TVOD, which PC users have trouble with. if you use something like Soundjam to encode, the file type/creator is MP3/SJAM and it's no problem for PC users..

“At any rate, that's not going to help a PC user who's already DL'ed a bunch of Quicktime format MP3's. is there a procedure or a utility that will allow the PC user to change to a usable PC format? i'm sure there is, but i'm pretty ignorant when it comes o PC stuff.”
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PC files don't have a type/creator. That's determined by what you have set in the File Associations preferences...that's accessible from one of the menus in any window in windows. Also I think you can get it in the Settings control panel.

The problem with the mp3's is:

1. No extension on the mp3. Windows, in a large way, is still too dumb to know what a file is unless you have the extension on it.

2. Or it's having trouble with a variable bit rate mp3. i.e., they were encoded with variable on and it's having a problem recognizing something that's say, 188 kbps bit rate, as opposed to a standard 192 bitrate.

There are many mp3 players for PC. Try Xing's...it's installed with Audiocatalyst and works quite well. Or do a search on download.com and experiment a bit with different ones.
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ps....MPEG/TVOD is a MOVIE format far as I know, and that may be confusing the PC (I know it's the type for mp3's in QT on Mac too). And wrong on the SJ type there...type/creator is ALWAYS 4 characters...

i.e., MP3 /SJAM, not MP3/SJAM. Umm...there are several apps that will convert the mp3 to a WAV format so it can be re-encoded on PC...look on download.com for "sound converter" or something similar.

Part of the basic trouble, too, is that quicktime won't handle mpg and mpeg well at all on Windows, I've tried this stuff and it's a royal pain, cuz Windoze wants to use Media Player to play it all. I can't play mpeg movies in Quicktime on a PC at all...never have got it to work to do that. Even setting QT as the primary viewer it doesn't play them. Sort of similar to the troubles we have on Macs playing AVI files. Seems I finally found a freeware app that played mpeg movies good in Windows - much better than Media Player - now if I could only remember the name of it :-) It's been 6 months since I messed with a PC.