I'm assuming you mean installing Office 2007 on an XP version of the Acer Aspire One. In fact although it comes with a health warning from other users, I have just installed Office 2007 on the solid-state-drive version of the Aspire, and while it won't break any speed records, you can certainly live with it. On a hard-disk version of the machine it should run a treat.
On my SSD version of the netbook, which I converted myself from the supplied Linux to XP (not something for the faint-hearted or anyone short of time, beware!), MS Word now loads in less than 30 seconds, which is respectable enough. Where the SSD version slows down is when you are writing to the drive -- reading is lightning-fast.
It is said that the freebie OpenOffice is faster because it has a smaller 'footprint' and is less resource-hungry. But if you have Office 2007 and are used to it, it will certainly run happily on a netbook, at modest speeds.