Tbh I doubt that you've got half a gig of setups. You only need to take the data\settings directory with you for setups. data\skins you probably want as well.
Unless you have a horrendous internet connection, I wouldn't bother with skins_x.
If you only need the setups then well you can fit A WHOLE LOT of them on the 512MB stick
I just checked I have 385 setups in the settings folder and the size is 92.6 KB
If you're only backing up setups, just stick them in a zip and email them to yourself. Assuming both PCs are on the net (and not even at the same time), it's a useful alternative if you don't have any other means to transfer the data.
Of course with LAN interfaces being standard in motherboards these days, a 30 pence patch cable would suffice also.
rar or zip them all up and upload them to rapidshare or megashare then take note of the link that it gives you.. go onto the other computer and download the zip/rar from there.
or just use a floppy disk or a cd/rw or email them to a msn or lycos account and then download them from there.
if u got a old hard drive laying around put it in an encloser ad then use it as external drive. i had an old 40 GiG lying around and it Now is my secondary backup drives P.S Enclosers are darn cheap if u buy then from http://www.newegg.com