So its September 2009, our first update fix is here for Windows 7
When we "Upgrade our WIM" or add stuff within its mounted environment we often then need to split the WIM across disks (rather than eating up expensive duel layer DVD) and In time we can have a drive fail or we just need the space and then later remember when we wish to Re-Update our OS install disk that our WIM is sadly multiple files.
You can re-compile a single WIM from multiple SWM files by the following method
Go to your Root drive, right click create a folder called TEMP
Copy all your SWM files into that TEMP folder
Open the command prompt (start, search, type, CMD, right click it and RUN AS Admin)
Copy this line off my page (or manually type it) and hit enter
to Past it, click the top left corner (of the CMD box) scroll down to EDIT and select paste, press enter
Now copy this text and paste it, or type it & hit enter
dism /export-image /sourceimagefile:install.swm /swmfile:install*.swm /sourceindex:1 /destinationimagefile:install.wim
Mount your new WIM file and check it for errors, then service the image how you needed to then re-split if desired.