Moving all files from iMac to PC

I'm not sure if this is the place for this post (I've searched a bit and read the backup/backup/backup post), but here's the situation:

I currently have an iMac (200 GB of 320 GB HDD used) with two external 1 TB HDDs (one with 460GB used and one empty). I'm switching to a computer with Windows 7 and I want to be sure of two things:

1. I move all personal files to an external HDD in a format that will allow relatively easy transfer to the new computer.
2. I erase all remaining personal information on the iMac HDD before it finds a new home. Especially saved passwords and stuff.

Here are the tricky bits:
1. Looking at the "Sage Advice for the New Mac switcher" post, I understand I may have complicated things a little. My iTunes music files are mostly on an external drive because they wouldn't fit on the internal drive. At some point in the past I wanted some files on the internal drive for more rapid access, so it looks like there are duplicates (I haven't gone through all, but I think/hope they're just duplicates). As a result, I see the files in location "/Volumes/External_Drive_1/iTunes Music/......" (460GB) but I also see 80 GB in "/users/(me)/music/iTunes". If I simply moved the files from the "/users/(me)" location to the "/Volumes/External_Drive_1" location would that basically be it, and it can be sorted out on the new system? Or do the files rely on some central function of iTunes to communicate all info (year, genre, artist, album, etc)? I'm hoping the new system can just look at all of it and say "Yep, this song goes here and that song goes there.".
2. I can't seem to figure out where OSX keeps my iPhoto files. If anyone knows, please give me a clue.

Of course, if there are other resources to find, just let me know. Or if I should just go to a Mac Store and have them sort it out, I guess that's okay, but I'd rather do it at home if possible.

Thanks in advance!

1) You should compare music folders to make sure which one has duplicates that can be erased and which one has different files that should be copied over to your external drive. You don't need iTunes to do this, just use two Finder windows side by side. Remember that if you have 2 folders of the same artist or album that have different songs, you can't "merge" them. You'll have to select the files within the artist or album folder on your internal drive and drag them into the one on your external drive. Basically, you're just combining files manually. Nothing complicated.

2) If you right click on iPhoto Library in your Pictures folder, you'll see an option that says "Show Package Contents". Choose that and you'll find your original photos in the folder called "Originals" and any modified photos in the one called "Modified". You can just drag them over onto your hard drive but you may be stuck with the way iPhoto has organized them.

Thank you! Moving the pictures was easy, and I'm working on the music files. It might be that I used an MP3 encoder (LAME) that deposited files on the internal drive. The ones there don't have any track numbers before the song titles. Anyway...

As for erasing personal information, passwords, etc., is it as simple as activating some SnowLeopard "wipe clean" function? Is it re-installation (I got the Leopard -> SnowLeopard upgrade disc)?

If you're selling the machine, you'll want to do a clean install of the OS - after you are sure you have all the data moved that you want.

To wipe your hard drive clean and install the OS, insert the install DVD and restart the computer. When you hear the startup chime, hold down the C key. From there you can follow these steps I found in a Google search:

How to Reinstall Mac OS X - wikiHow

Thanks again! For some reason, I didn't look at Google and I feel kind of stupid now. In any case, that's exactly what I was looking for.