One project for a friend ends (the sub £400 SFF) and another begins...

About 6 or so months ago I built a friend a computer with a RAID 1 array of two 500GB Samsungs - he didn't have cash enough to buy even the cheapest boot HD after I'd talked him into a Q9300 and 4GB of DDR3 - so the OS & apps went on it along with his "live" data (he runs multiple externals for backup - but, and this is where it gets sticky, they're all full now)

The thing is, being quite the worrier (and perhaps rightly so) he wants to ensure that when his computer comes out of freight on the other side of the world (he's emigrating to Oz) that all his data won't be kaput. So, he's gone and bought a new 500GB HD and is waving it at me earlier going
...and I'm looking at him like

...and so, the question(s): Can this be done? How? Probably best to write an image first (he's got Acronis Director 8 or 9 I can't recall) no?

Eeek!

Assuming your using that standard raid tools in XP you should be able break the raid in disk management, whip one of the discs out, replace it with the new disc, import new disc in disk management and rebuild the raid.

If you ever need to rebuild from the spare, add it and another empty disc, import them and rebuild them in disk management.

At least that's how I remember it works from the XP course I took about 5 years ago...

I don't have any idea how it goes under Windows, so this may be of no help to you, but I don't see why all RAID wouldn't take the same mentality:

Under Solaris with a ZFS mirror, if you yank a disk out the mirror is considered degraded. If you put a new (or the same disk I think) back in, it will start to automatically resilver the new drive (because it's taken the logical place of the old one). Note that you may have to resilver the old drive when you put it back in...

Why not get a USB caddy for the drive and then just image the system to the HDD

That way he has a full image

Should be fine to pull the mirror and put a new drive in. It'll rebuild itself.
It's always worked for me (although usually a drive is dead).

Doing an image with Acronis would be faster though.