Upgrade Note: Running Windows XP SP3, 512 MB is adequate but sluggish. To run a lightweight Linux distribution (like Puppy or antiX) or even a heavily optimized Windows 7, you must max this out to 2GB. Be aware that the Intel 915PM chipset does not recognize individual 2GB DIMMs.
Battery technology at the time was modest: sony vaio pcg-4g1l specifications
A deep technical specification often overlooked is the embedded controller chip (EC) firmware logic regarding thermal throttling. Upgrade Note: Running Windows XP SP3, 512 MB