AA1 9inchers UMPC AFAIK has 512 built-in and one SODIMM slot capable of 1gig only. My old MSI U100 has 1gig built-in and 1 SODIMM slot capable of 1gig.

Vendor will honor warranty if they will be the who will install it to your UMPC. Some shops do not restore warranty seals after the upgrade - I did HDD upgrade myself from 250 to 500gig and shop told me that there will be no problem with warranty claims as long as there's no physical damage.

see attached with my HDD upgare-i found out that U123H has only one memory slot and no built-in.