@JanJan: You can place the game onto a USB flash drive and play it from that - doesn't need a registry entry, WoW is super-portable. Set config to Window, 800x600 and you are set!
You may have 2 problems though:
1) Firewall - I've to juggle our networks to get to the unlocked one as our internal one is.. internal

2) Addiction - eventually, you will do fishing or something easy.. and then you do something like crafting.. then questing.. then leveling.. oh oops!
+1 Drain - you can save tenths of gold by buying only the real spells of your given spec, eg. if you are frost mage, you don't need scorch, if you are a feral druid, wrath/SF no point.