There may be a compatibility if the pin count, voltage, and any buffers, etc between the newer PC100/133 and the older standard PC66; if you can get the original PC66 of the proper capacity, that'd be OK.
Somewhere I had a page link saved or maybe bookmarked in one of my several Mac browsers, that had information on compatibility of newer chips to replace older ones.
And some of these even with modern hardware can be flakey or damage the computer. Or work just long enough to confuse the user once they do start to fail. A cross-compatibility of 204-pin RAM that may work in both MacBook and iMac, over a year or two, can be a problem; in that one set runs hot and uses more power in the portable. But is OK in the iMac.
{The FW clamshell iBook G3 uses the same series upgrade RAM the first White iBook G3 does, or at least when I upgraded the chip in mine, it took a PC100/66 512MB, to max at 576MB total. Later I sold it to a really old guy, as his first computer. He wrote letters online and did email. I provided a few years support to help him learn about Macs. That sale included the box and all the original kit, plus later OS X upgrade discs.}
Anyway, it does help to seat the RAM fully yet carefully.
Removing RAM may also be a matter of light force, too.
Glad to hear you got some activity out of the exercise.
Good luck & happy computing! ๐