You should be able to affordably upgrade the RAM to correct specs, and with both pieces
of memory correct, there should be no bottleneck in that aspect of its function. Quality RAM
of correct specification should not cost more than $10 per piece; with these specs:
example from OWC macsales.com with correct specs detailed:
another company I've dealt with by mail, with good results fair price incl shipping, asks $12. ea
1_0G-PC2-SO5300 - oempcworld macbook configurator results (mine has 2 of these)
The next greatest and affordable (if you can find one) upgrade would be to replace the
original rotational hard disk drive with a faster spin-rate, as that can add speed where
temp files and virtual memory (re: drive read-writes are involved) of significant gain.
My MacBook1.1 (same first model as yours, but with 2GB RAM + 160GB 7200-RPM HDD)
moves along quite nicely, compared to 1GB RAM and slow original spin-rate hard drive.
In any event, your computer should work correctly with the best quality; prices are lower now.
Some locations, including 'garage sale online' page at OWC may have these for much less
since they get tested-good/used-pulls from working computers, on occasion. An Apple
specialist may have some on-hand from an upgrade that were working fine. 2x shouldn't be
over $24. total for both; that's low retail new if ordering from supplier.
Doubt your computer would be damaged from trying the incorrect spec 2x 2GB RAM, so
long as 'static shock' doesn't toast the electrical components during handling of them...
Note: Niel said, The computer won't start up if more than 2GB is installed.
Good luck! 🙂