iTunes works just fine for me with Vista 64, and I would assume Vista 32 as well. Vista supposedly has much better support for audio playback than XP.
Do you have your RAID array in the XP computer now, or using a separate NAS/fileserver? If indeed it's all on one machine, then I expect that you'll need a different boot drive for the OS, as with 4 TB I don't believe you'll be able to use MBR. Just something to look in to. Also, iTunes tends not to do well with WAV files (see the archives on this), because iTunes keeps the tag data separate from the files themselves (since WAV has suboptimal support for tags). Everything will be OK as long as you don't change the filenames or paths.
I mention this because to do as you say, you'll need to back up your 1.5TB of files (I do hope you have backups), expand your RAID array, rebuild/initialize the newly expanded RAID, partition and format the new space for Windows (and here's where you may need to consider GPT vs MBR for that size), and then copy the files from your backup back onto the newly enlarged RAID. And they'll need to have exactly the same path/filename as before, or otherwise the album/artist/song information that iTunes keeps separately from the files will lose their connection.
I assume that you've already thought about some of these challenges, but I figured it was at least worth mentioning. You might actually find it a lot simpler to convert the WAV's into Apple Lossless, which would probably give you comparable music storage ability in 2TB that you'll get with WAV in 4 TB. It will still work with the iPod, and you'll have better tagging ability. Some people claim that they hear an audible difference between Apple Lossless and WAV, but I've never heard it. I used to have files in WAV several years ago, then I converted to a few Apple Lossless and most FLAC, and I've never looked back.
Just my 2 cents.
Michael
Do you have your RAID array in the XP computer now, or using a separate NAS/fileserver? If indeed it's all on one machine, then I expect that you'll need a different boot drive for the OS, as with 4 TB I don't believe you'll be able to use MBR. Just something to look in to. Also, iTunes tends not to do well with WAV files (see the archives on this), because iTunes keeps the tag data separate from the files themselves (since WAV has suboptimal support for tags). Everything will be OK as long as you don't change the filenames or paths.
I mention this because to do as you say, you'll need to back up your 1.5TB of files (I do hope you have backups), expand your RAID array, rebuild/initialize the newly expanded RAID, partition and format the new space for Windows (and here's where you may need to consider GPT vs MBR for that size), and then copy the files from your backup back onto the newly enlarged RAID. And they'll need to have exactly the same path/filename as before, or otherwise the album/artist/song information that iTunes keeps separately from the files will lose their connection.
I assume that you've already thought about some of these challenges, but I figured it was at least worth mentioning. You might actually find it a lot simpler to convert the WAV's into Apple Lossless, which would probably give you comparable music storage ability in 2TB that you'll get with WAV in 4 TB. It will still work with the iPod, and you'll have better tagging ability. Some people claim that they hear an audible difference between Apple Lossless and WAV, but I've never heard it. I used to have files in WAV several years ago, then I converted to a few Apple Lossless and most FLAC, and I've never looked back.
Just my 2 cents.
Michael