Hello,
 I have been able to produce the following:

Microsoft Windows XP [Version 5.1.2600]
(C) Copyright 1985-2001 Microsoft Corp.

C:\Documents and Settings\yemi>irb
irb(main):001:0> File.split("C:a/b")
=> ["C:a", "b"]
irb(main):002:0> VERSION
=> "1.8.4" 
irb(main):003:0> exit

C:\Documents and Settings\yemi>irb
irb(main):001:0> File.split("C:a/b")
=> ["C:a.", "b"]
irb(main):002:0> VERSION
=> "1.8.3"
irb(main):003:0> exit

C:\Documents and Settings\yemi>irb
irb(main):001:0> File.split("C:a/b")
=> ["C:a.", "b"]
irb(main):002:0> VERSION
=> "1.8.2"
irb(main):003:0> exit

So it seems to have been a bug that was corrected in 1.8.4
Yemi Bedu

P&R Fasteners
325 Pierce St
Somerset, NJ 08873
732-302-3600
-----Original Message-----
From: Berger, Daniel [mailto:Daniel.Berger / qwest.com] 
Sent: Monday, March 20, 2006 5:27 PM
To: ruby-core / ruby-lang.org
Subject: Re: File.split on windows box appends a '.' to directory name

> -----Original Message-----
> From: Jim Weirich [mailto:jim / weirichhouse.org] 
> Sent: Monday, March 20, 2006 3:21 PM
> To: ruby-core / ruby-lang.org
> Subject: File.split on windows box appends a '.' to directory name
> 
> 
> I'm exploring file path manipulation and discovered that on a 
> windows box:
> 
>  >> File.split("C:a/b")
> => ["C:a.", "b"]
> 
> I would expect ["C:a", "b"], which is indeed what I get when 
> running on 
> Linux.
> 
> Is this a bug, or am I missing something?

Works for me:

irb(main):001:0> File.split("C:a/b")
=> ["C:a", "b"]
irb(main):002:0> VERSION
=> "1.8.4"

What version of Ruby?

Dan