I was able to update to iTunes 10.5 on my Dell laptop (XP) and my brand new MacBook Pro 

) but on my desktop, Dell XPS running Vista, it keep failing. (I tried about 5 times.)  And unfortunately that is the computer that my iPad1 is synced to at this time!! (It is dying, that is why I just bought the MacBook Pro.) It said if the update failed to download the update only from Tools and manually install.  I did that, but when I got to the install part, it looks like a new install of iTunes.  I was afraid I would lose everything in my current iTunes if I did that so I canceled.  I don't know what to do now.
I wanted to have the MacBook Pro be the computer the iPad syncs to, but got a little nervous when I tried to transfer it and it said it would wipe my iPad. Does that just mean the photos or all the apps and content of the apps too??  I am not technical at all and really am afraid of messing something up. Can I update my iPad on the mac even though it is not the one I normally sync to?  I am totally confused about what to do at this point.  Any suggestions would be appreciated.  Thanks!