dir /b/s *.txt
searches for all txt file in the directory tree. Before using it just change the directory to root using
cd/
you can also export the list to a text file using
dir /b/s *.exe >> filelist.txt
and search within using
type filelist.txt | find /n "filename"
EDIT 1: Although this dir command works since the old dos days but Win7 added something new called Where
where /r c:\Windows *.exe *.dll
will search for exe & dll in the drive c:\Windows as suggested by @SPottuit you can also copy the output to the clipboard with
where /r c:\Windows *.exe |clip
just wait for the prompt to return and don't copy anything until then.
EDIT 2:
If you are searching recursively and the output is big you can always use more to enable paging, it will show -- More -- at the bottom and will scroll to the next page once you press SPACE or moves line by line on pressing ENTER
where /r c:\Windows *.exe |more
For more help try
where/?