Why buy 2nd hand when for $498 or $598 you can get a new Lenovo 3000 C200 or N200. They are really very good lappy's, see here:
http://www.iceinspace.com.au/forum/s...ad.php?t=29085
Apparently some stores still have a few stocks left, mainly the $498 version. Which is still a very good performer and a whole lot more power packed than something like the ASUS EeePc.
Phoning around some stores may find you one of these little gems.
Edit:
forgot to say baring that MSY is about the cheapest place for Laptops.
http://www.msy.com.au/notebook/notebook.pdf
And... if your scope needs a RS232 port (serial port) then maybe a lappy that has one...which is probably not easy to find a Lappy with one these days. In any case you can use a RS232 to USB converter. I'm using one from Jaycar and it works fine.