The reason you recieve "High speed USB Device pluged into a non high speed USB Port" is because the port you are using is USB 1.1. The iPod Recommened requirements are to have USB 2.0. Now this doesn't mean that it will not work, but it means that transfering data from PC to the iPod will be slower.
(USB 1.1: 12mb/s USB 2.0 480mb/s Firewire 400mb/s)
In order to make sure that your other PC has USB 2.0 then do the following:
Click Start > Run > msinfo32 then click ok
--> Click + beside Components
--> Click USB
You should see 1 of 2 things
--> USB 2.0 Root Hub
--> Standard PCI to USB Enhanced Host Controller
Take a look at the screenshot so you can see what it will look like
In your folder where you have your iTunes Music folder stored
(Default C:\Documents and Settings\%user name%\My Documents\My Music\iTunes\) you will have a file called iTunes Music Library.xml and iTunes 4 Music Library.itl. If you copy these files to the same location on the other PC you "should" have all of the track information loaded back in. You can take a look at an ID3 Tag viewer before transfering the files over to your other PC to make sure that iTunes has written the tag information to the mp3s.
If you do connect your iPod to your new PC iTunes will open up and say "This library is already synched with another iTunes Music Library. Would you like replace the current library with those from this iTunes Music Library?"
Yes or No
If you say yes your iPod will be replaced with your blank library. If you say no then you can set your iPod to a Manual update (Right click iPod in the Source List > iPod Options > Manually manage songs and playlists > Yes > Ok)
I am thinking whether or not to develop a small application used to backup music from the iPod onto the PC but I am unsure about this simply because of the RIAA and the copyrights on the songs. If I do do this then all music will actually be deleted from the iPod after it is backed up.
If you are worried about loosing your music when you connect your iPod then do this.
Putting iPod into Disk Mode
1. Plug the iPod Power Adapter into an electrical outlet and connect iPod to the power adapter.
2. Toggle the Hold switch on and off. (Set it to Hold, then turn it off again.)
3. Press and hold the Menu and Select buttons until the Apple/iPod logo appears, then release them. This resets iPod. When you reset iPod all your music and data files are saved, but some customized settings may be lost.
4. When the Apple logo appears, immediately press and hold the Play/Pause and Select buttons until the Disk Mode screen appears, saying Ok to Diskconnect with a Check Mark.
5. Disconnect iPod from the power adapter and connect it to your computer.
In My Computer double click on your iPod that is listed (Will say either Removable Disk or the name of your iPod)
You can copy your iTunes Music folder onto your iPod. Then use
this article from apple to manually unmount the iPod. Disconnect it from your computer and connect to the other PC and take the iTunes Music folder from the iPod and place it in your My Music\iTunes folder.
Matty