You can try to update system in runtime through installer (I haven’t checked this).
However, if you just have an upgrade WIM image and you want to apply it remotely, the things are slightly complicated.
In this case somehow you have to bring your current Windows offline and update it completely.
It’s feasible even remotely, but you have to implement your own upgrade procedure.
I’ve checked the essential parts of the steps below and they will work on any Windows (embedded or desktop).
Prerequisites are:
Windows 7 syspreped and fully unattended image which you want to upgrade to. After deployment it must start without any questions, connect to network and automatically offer remote access. As usual, you can sysprep an image with answer file to achieve such behavior.
Prepared Windows PE files. This Windows PE must create ramdisk after start and perform upgrade steps (see details below).
Enough space on target device to fit upgrade image plus Windows PE files. At least 1
GB RAM is highly recommended, however, Windows PE 3.0 x86 will successfully start with 512
MB RAM.
One sample target device to deeply and intensively test the procedure. You need such a testing because if something goes wrong during remote upgrade (for example: network card driver not found) the system will be completely out of order.
The procedure is:
Remotely copy Windows PE 3.0 (or later) files (I’ll explain the requirements to this WinPE image further) directly to target Windows XP system drive root. Copy your upgrade WIM files as well.
WinPE 3.0 (or later) requires NT 6.0 boot sector, so modify boot sector (including MBR) to version 6.0 using bootsect.exe (copy it to target system as well).
Reboot system.
System boots up Windows PE and an upgrade script starts. Now the upgrade script should automatically remove Windows PE files (it’s possible because it starts from ramdisk) and old
OS files, but it must keep upgrade WIM files.
If upgrade
OS image requires different partitions layout, your upgrade script can shrink current partition, then create and format new one, then move WIM to it, then delete old partition and create required layout.
Now the script applies an upgrade WIM and creates boot data if necessary.
The script reboots target system.
Target system starts automatically and goes through Specialize and OOBE System passes unattended. It automatically brings up network connections and becomes accessible remotely.