[reboot]

It's not in c:\windows...the actual driver for it will be buried in c:\windows\inf or c:\windows\inf\other
If those folders are hidden when you browse for it, just type it in manually. It could even be in c:\windows\inf\other\modem or c:\windows\inf\other\intel\modem...get the idea?
Use Explorer to view all, including system and hidden files, then you'll have a good idea what you need to type in the path to find it.