find / -name filename 2>/dev/null
find will automatically work recursively through all the directories below the one(s) you give it to start with (in this case / - the root directory) and -name says to search by name (you can use wildcards such as filen*) - there are many ways of searching with find.
The 2>/dev/null command is only really necessary if you execute the command as a non-root user (otherwise the results will be drowned in "Permission denied" error messages). 2 is the "file descriptor" for the standard error stream, and the > redirects the error messages to /dev/null (otherwise known as the bit bucket.
Oh, and bashrc is normally .bashrc (the leading dot indicates a hidden file).
Hope this helps,