That's a pretty heft question actually. I mean, are you happy with the deployment of the two Operating Systems and simple want to know how to migrate user data? Or are you needing help with the actual deployment process for the new Operating System? Or are you trying to figure out how to deploy and configure Windows 7? Regardless, all of these are huge topics and probably not things that Altiris/Symantec can actually assist with directly. So, please define what you are actually asking.
To preempt the possibility of the "deployment" side of things, note that you can STILL use the "Scripted OS Deployment" job - but set it to a "Windows 7" job after you upgrade DS to the appropriate Service Pack level (may as well have SP5 installed - it works). With this, you can STILL run the same SYSPREP process you did for Windows XP, and even capture the image using the same type of DS job, and in the Altiris IMG format (in fact, I recommend it if you're not familiar with ImageX yet). The only extra things to be aware of:
a) Pros: Windows 7 has a massive list of built-in drivers that can make most hardware deploy and boot without playing with any drivers - great for just testing a deployment. Moreso, it doesn't have the HAL issues of XP, so you can use a single image to deploy to a single core, multi-core, system, with different mass storage controllers, everything. It's also massively faster and far more customisable than Windows XP.
b) Cons: Boot Configuration. You'll likely see WinLoad.exe BCD errors until you get this sorted. The "Scripted OS Install" may let you down here and require a "Run Script" task to fix it.
If you want to play with Windows 7 by scripts and tasks - so you can see what's going on every step of the way, then you may wish to see my blogs:
http://www.symantec.com/connect/blogs/murrayw
You'll see the WAIK actions, with SIM to build the XML, the scripts required to deploy the system, and the tasks required to make everything work - including injecting drivers.
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If you're asking about migrating existing users, you may wish to look at the "User State Migration Tool" (USMT) from Microsoft. You can script it and it does a pretty good job. My recommendation (and long standing best practise) is to have a second partition on each system where I use "Folder Redirection" for the user's data... that way I can back that up or re-deploy and just ignore the system and applications.
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As for building the Windows 7 system and migrating settings, policies, etc... that's going to take some trial-and-error and much Googling.
I hope that helps.