Hi Kev
You were luckier than me - maybe - you managed to install the download but at least my Boot Camp is still working.
How did you manage to install it?
Each time I tried to install SP3 it told me there was not enough space and I needed to free up 4.4MB of disk space - even though I have 20GB of free space on the drive.
Now I have given up and switched off Windows Automatic Updates.
I figure someday soon, Apple will give us an upgrade download to Mac OS X 10.5.4 that will allow the successful installation of Windows SP3 within Boot Camp. Until then we keep soldiering on.
Must say I'm a bit disappointed with Apple that they expect their customers to solve their own problems.
For what it's worth, trying to upgrade SP1 to SP2 also required 4.4MB more free space. It required the SP2 disk to install. Maybe this is the same.
I also have a Windows XP PC laptop that is upgraded by downloads to SP3 so I won't be buying the program disk for Boot Camp.
Best regards
Charley