Thank you very much for your reply!
Unfortunately, when I browse to the driver files (.inf .cat and .sys files) Windows actually doesn't SEE them, meaning I can click on the files and say OK, but when it comes up to the list of devices that those files are supposed to support, the list is blank. Typically I would assume this means that the drivers aren't for Windows 98, but according to the description, they are.
Here's a link to the topic I'm refering to (if you feel like doing a little reading). After the first couple of irrelevent posts about remotely resetting the modem, you'll see that many many people are having the same exact problem I'm having with Windows 98 and this particular series of RCA modems. Near the bottom, somebody explains that Windows 98 doesn't see these drivers, but they can be "installed manually".
I'm getting really close to upgrading to XP, but it seems to me that this is indeed possible. But if it can't be done it can't be done.