I think media replacement is perfectly valid

I agree. You bought it once. There are no other outlets to buy it from. Therefore download without guilt!
or find a random person on the programming team and send them a $10 check and a thank you note. They don't get enough of those.

Can't find it anywhere? I question that... If you mean can't find it in your house, that's tragic, but it's not that expensive to get another copy.
http://www.amazon.com/Star-Wars-Knights-Old-Republic-Pc/dp/B00006IR62/ref=sr_1_7?ie=UTF8&s=videogames&qid=1258340811&sr=8-7
http://store.steampowered.com/app/32370/
[url=http://www.direct2drive.com/8380/product/Buy-Star-Wars:-Knights-of-the-Old-Republic-Download]http://www.direct2drive.com/8380/product/Buy-Star-Wars:-Knights-of-the-Old-Republic-Download[/url]
http://video-games.shop.ebay.com/?_from=R40&_trksid=p3907.m38.l1313&_nkw=star+wars%3A+knights+of+the+old+republic&_sacat=1249
...In general, I hate piracy. I hate what it does the gaming industry (People complaining of invasive DRM, take heed: It wouldn't exist without the threat of piracy!), and I would never condone it, even if you exhausted every possible other option first.

Holy crap! New retail copies of KOTOR are going for $90 these days?! Glad I got my copy back when they were only $20 or so. At least the DD versions are at a very reasonable price.
Riiiight. Might want to take a look at all the artificial roadblocks printer cartridge manufacturers threw up to keep third-party cartridges from working with their printers (including the DMCA suit that Lexmark filed). Of course, I'm sure all those things were just to combat the rampant pirating of printer cartridges. ;)

I can't find it at my house, not online.
I don't lik piracy if the game was never paid for, however this is different, as I already paid my $30 for the game (price when I bought it)

Personally I'd buy it again as opposed to supporting the people who profit off of piracy (such as the people running certain servers/sites that aid in piracy... (who make money off of the adverts displayed when you search, etc.) and the relatively cheap price at which the game can currently be purchased at can be considered as the charge for replacement media that most publishers would levy anyhow...

You should download it. You work hard for your money, and there's no reason to throw it down the drain for digital media that you've already paid for. It's simply unfortunate that you didn't already make a backup copy for yourself, but thankfully, the internet has a backup copy for you, unlike the party you purchased it from in the first place.

I don't think downloading illegal copies off the internet is unethical since you already paid for one legitimate license. If you're still iffy, though, you can find someone else who has legit disc and copy the game files from that person.

Do you have any proof you bought it? I'e downloaded media for games where I nowdays only have just the box or manual for, I figure I can claim it as a backup and wave the manual in people's faces if they complain

I'd do it, but then again I'm a virusphobe. Hell, if you bought the game and can't get it to work, just download a cracked version. I did for Halo...
EDIT:
Oh, and FUCK NO, it is NOT immoral! You bought the game, you should be able to get the file you want.

Morally speaking, no. You paid for it.

It may not be legal, but I fully support this action. Unless it's a version built to run on newer computers by a different team (like what GOG does), in which case buying it would be the best course of action.

Yes, it is immoral if you're torrenting it, because then you're enabling other people to pirate it. YOU DO NOT WANT TO ENABLE OTHER PEOPLE TO PIRATE IT.
If you have a friend who has a copy, and he copies it for you, that's more acceptable, because you aren't attributing to the piracy of others.

Err... If you have a friend with a copy, why not just borrow the friend's copy? Quicker that way.