Q: MacBook 2007 boots up with 1 gb of ram but not 2 gb

Do you hear any beeps?

Sounds like either one of the modules is bad, or one of the slots is bad.

Have you tried with one module at a time to test?

Where did this other module come from?

bad ram, damaged ram chassis, ram is not properly seated.

reboot with 1GB and reset PRAM and boot normally

https://support.apple.com/en-us/HT204063

then shut down and install RAM using procedure outlined here

MacBook Pro: How to remove or install memory - Apple Support

if the 2nd chip fails take the 1st RAM chip out and try the 2nd in the slot where the 1st RAM chip was

if the single RAM chip failed it's likely bad RAM.