2GB is prolly not enough to 5-box without thrashing.

here's the basic math to determine if you'll thrash.... thrash happens when you exceed 80% physical memory used:

80% * memory > OS + N * WoW

memory: 2g
OS: xp == 500m, vista == 1.2g
N: 5
WoW: 500m

xp:
80% * 2g > 500m + 5 * 500m
1.6g > 3g --- fail

vista:
80% * 2g > 1.2g + 5 * 500m
1.6g > 3.7g --- fail

so, no matter what, you would be trashing pretty much constantly. this would crush your performance.

this also shows that you can 5 box on xp with 4g of memory, but not on vista. get vista64 and crank your memory to 8g+ and you'll be loving life.