I don’t know if it’s possible to upgrade online and I’d avoid it to be honest and buy a physical disk.
However there are a few things to note when comparing prices:
Microsoft Windows Vista Home Premium – Upgrade package A bargain at only Â£65 but you must install on a system that already has Windows XP or Windows 2000 on it. This upgrade *should* work with the XP Home installation that came with the NC10.
Microsoft Windows Vista Home Premium – OEM This is the full version (not an upgrade) but as it is an OEM edition it is tied to the motherboard that you install it on. Price is Â£83.
Microsoft Windows Vista Home Premium – Complete package This is the full version with no tie to hardware so you can uninstall it and then reinstall it on any computer at a later date. Most expensive at Â£134.