Liberty:
Well I don't have any mac experience but I just a got a new dell with Vista on it. and I have to say I'm not impressed. Not because the system is hard to use it's reallly just the about the same as XP but because somehow I don't have a lot of thigns like powerpoint that I did have on my XP one. I did just get it so it maybe moslty me jsut hating it while I figure out how to use it but despite supoosedly beign able to make videos on it ect. I find it's media programs fairly useless right now. I loved the Windows media player I had on my XP. It was simple basically copied and played muisic which is all I wanted. I'm also haveing trobule transferring files from my XP to Vista. I'll try to transfer music files so I don't have to recopy everythign and it will say file is "corrupt" maybe it's just because it's so different from windows(that's what they claim) but I'm not enjoying this particulary during finals. So read the reviews and decide what you think will work best for you but save backup files as well as a way to get to them if you get Vista.
Some things that might help your problems.
1) If you have an install disk or a full system backup disk (that includes your operating system) from your old computer you can "downgrade" your new computer to XP and run that instead of Vista.
2) If you are missing Word, Powerpoint, Excel and the like it is because your new computer didn't come with "Microsoft Office". This is separate from the operating system (Vista or XP). Some computers include it, some make you purchase it separately. If you are a student it is not that expensive (my Office Mac was $150 with student ID) or your school may even supply a copy free. Your other option is to go open source; check out www.openoffice.org (I recommend this only to people very experienced with computers; install and operation are NOT always intuative and frequently involve getting into areas of your code that could destroy your operating system).
3) Apple offers iTunes as a free music player for both macs and windows PCs (you need not have a mac, ipod, or download from iTunes to use it...though I now qualify on all 3 counts....). I prefer it over windows media and the other players for playing my downloaded, uploaded, and CD music. You can install this on both computers. Once you have your library in itunes on your old computer it should be easy to transfer it to the new computer without the file corruption issue. iTunes even has a nice library import feature that makes this easier; especially if you are connecting your computers directly for this. (as far as I know mp3 and mp4 files have not changed formats, so it's odd that you are having problems!).
BTW: Vista was Microsoft's attempt at "copying" the usability, features, and stability of Apple's OS X (they even tried to make it look similar). They failed miserably and it won't even run on most computers!!! ;) Meanwhile Apple's new OS X Leopard is getting rave reviews with tons of new features and finishing touches... (I wanna upgrade! whhaaaaa!)
O, and apparently Microsoft can't pay companies enough to associate with them anymore... Yahoo just turned down a pretty massive buyout offer despite having issues of their own. hehehe. Ok, now I'm spreading gossip and propetuating the mac user stereotype, so I'll stop ;)