In the Win32 world of forward slashes "\", if the path string of the file sytem commands contain an "escape char", i.e. \r, \n, etc then the path to the file is not read correctly by PHP3. 
I.E. $cat=fopen("c:\home\result\new\xxx.dat","a");
is read as C:\home
esult
ew\xxx.dat.

This is not that important, the work around is simply, don't use escape characters in the path string.
just if you get around to fixing it.