How much information data have you into PC?
If you have less than 1 or 2 GB in documents, few pics), is better you get a USB drive or a pendrive.
If this information is more than 2 GB, is better get a harddrive.
If you have from 2 GB to 7 GB use a DVD rewritable, and/or if you have more than 8 GB, you can buy an external drive with capacity according to you data with connection USB, if you do, please get it on 2.0 port version, 1.1 is too slow transfer of data.
Probably the minimum capacity is of 20 or 40 GB. Check in ebay, may be you need an adapter in order to conver to SUB if this a IDE interface.
http://cgi.ebay.com/10GB-2-0-USB-2-5-Portable-External-Hard-Drive-10-GB_W0QQitemZ230213641517QQihZ013QQcategoryZ99247QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
Bye,