search entire drive say c:

[McColgst]

>    ROOT = "c:\\"
>    fname = "abc.txt".lower()
>    for p, d, f in os.walk(ROOT):
>      for fn in f:
>        if fn.lower() == fname:
>          print os.path.join(p, f)
>          # break

I think you mean

print os.path.join(p,fn)

-sean