Is it common for Office 2008 (Word, especially -- hangs on splash screen for at least a minute) to run slow on a MacBook with 512MB RAM?
Here are the precise specs from OWC Mac Specialist at Find the latest Performance Upgrades, Firewire and USB Hard Drives, SATA, Memory, Laptop Battery, and more at OWC
1.0GB PC-5300 DDR2 667MHz SO-DIMM 200 Pin... (5300DDR2S1GB) at OWC
Dump the 512MB as matched pairs perform best.