Do u have right privilege to process files?
if u got correct settings on privilege then try the statements below:
set fso=CreateObject("Scripting.FileSystemObject")
set f=fso.OpenTextFile("c:\log.txt", 8, True)
f.writeline(oUser.Fullname & " ~ " & (date()) & " ~ " & (time()) & vbCrLf)
f.close
set fso=nothing
hopes to help.

No Pains,No Gains.:D