[Matth]

There are a lot of arguments, and different policies, on computer upgrades and warranty, at least on things which ARE in a zone documented as user-upgradeable in the manual.

And PS. Kicking myself for buying a SD in Tesco (Sandisk Ultra 2GB) - 7dayshop had them a lot cheaper.
Autotest result (found in event viewer) had this as 3.2MB/s read (not that impressive, an old Tevion 1GB managed 4MB/s) and about 8GB/s write (now that IS quick).

Readyboost doesn't ADD memory, but it can boost boot, load and shutdown speed, when readyboosting over 512MB or 1GB (diminishing returns if you have 2GB RAM or better). Advantage of SD card readyboost (over USB drive), is that if you don't actually use the reader for anything else, it's fit & forget with no sticky-outy bits.

The other problem choosing a card, is that SDHC class, 100x/133x/150x/200x speeds or any claimed MB/s sequential transfer rates, do not always translate directly to readyboost performance profile's 4k random read and 512k random write - particularly for the 4k read, if the card has been tested anywhere and is poor for access time, that probably means poor for readyboost.

For JUST readyboost, 2GB seems adequate, though in tests, they often pair a 4GB with 1GB RAM - if you store other things on it as well, then you may want to go higher