As i am very satisfied with my OpenSolaris on this Toshiba, i decided to upgrade with 1GB of memory. This is the reference i just

order: CORSAIR 1GB DDR2 (SO DIMM) 533Mhz PC2-4200 - VS1GSDS533D2

Kingston ValueRAM SO-DIMM DDR2-SDRAM 512 Mo - KTT533D2/512  is for laptop. (The above in blue was for desktop computer)

You can see if you have room for memory (DIMM) in the laptop with the following command:

#prtdiag -v |more
System Configuration: TOSHIBA TECRA M3
BIOS Configuration: TOSHIBA Version 1.40 11/15/2005

==== Processor Sockets ====================================

Version                          Location Tag
-------------------------------- --------------------------
                                 uFC-PGA Socket

==== Memory Device Sockets ================================

Type        Status Set Device Locator      Bank Locator
----------- ------ --- ------------------- ----------------
SDRAM       empty  -   DIMM 0              CSA 0 & 1
SDRAM       in use -   DIMM 1              CSA 2 & 3