[tlug] Installing Windows after installing Linux

[Dave M G <martin@example.com>]

TLUG,

Despite my intentions, I find I am now in a situation where what I need 
to do is repartition my hard drive and put Windows on.
I briefly considered buying a second hard drive for Windows. But the 
drive I have is 250 GB, of which I'm unlikely to ever use more than 100 
GB. And the cost of hard drives is enough to make me think it's not 
worth it.
So what I would like to do is shrink the current Linux/Ubuntu partition 
to free up about 50 GB of space for Windows.
That part seems easy enough. All I need to do is boot one of many 
versions of a Linux Live CD, and use one of many command prompt or Gnome 
based partitioning applications.
The tricky part is that I worried about Windows over writing GRUB or 
creating it's own Master Boot Record or something and me not being able 
to get at my Linux parition anymore.
It's been years since I've attempted anything like this, so my memory is 
hazy, but I do recall that Windows thinks of itself as the one and only 
OS on the system.
Looking on the web, every piece of advice I see is about installing 
Windows first, and then Linux second, which is as easy as pie because 
every modern distribution of Linux seems to smartly handle multiple OS 
detection.
Perhaps I'm using the wrong search terms, but I can't find any good 
advice about the other way around - starting with Linux and installing 
Windows second.
So I'm looking for warnings and advice about how to do this. 
Particularly with regard to how GRUB will be maintained.
If people scare me enough, I may go ahead and buy that second hard 
drive. But if I can be assured that installing Windows can be done 
without adversely affecting my Ubuntu installation, then that would be 
the preferred way to go.
--
Dave M G