I've made quite a few images with Thin PC, it's an amazing version of Windows that really shines with the feature set it has out of the box.
This week I tried seeing how small I could get it. My existing images of Thin PC are quite large, with user content and extras ranging in the 40-60GB mark, I use it as a portable OS using VHD boot from my Seagate 7, ideal since I can be anywhere and boot a machine quickly with my apps ready. Plus, if I want to test different versions, with VHD I can add as many entries as I want. (I stick to Microsoft's bootcode, no grub4dos for me)
Using Win Toolkit, I was able to reduce the install footprint of Thin PC to around 2GB. I did this by removing mostly useless legacy drivers (which makes sense since it's a replacement for Windows For Legacy Devices) which included TV Tuners (Seriously?, TV Tuner drivers?), Modems, PCMCIA Drivers etc. I went through and removed tonnes of components. Once complete my lowly E2180 chugged away for about an hour or so and removed all the junk I wouldn't need.
As it stands right now I have a 3GB fixed VHD with about 500MB free, since I installed a few apps for testing. What is interesting, for very basic use, I had it running in VirtualBox with only 512MB of RAM. So it ran "ok" but not great. Keep in mind, my E2180 does not have VT so I'm using a very slow virtualization that only support 32 Bit OS. Later today I'm going to test it on my other laptop from USB and see how it fares.
Thankfully I saved some code from one of the forum threads here when I originally made my Thin PC images, I'll share it here as well since I've tried to find it since but couldn't.
If you want to boot the VHD from USB, you need to change some priorities when it comes to USB loading drivers.
reg.exe add HKLM\System\CurrentControlSet\Control /f /v BootDriverFlags /t REG_DWORD /d 0x6 reg.exe add HKLM\System\CurrentControlSet\Control\PnP /f /v PollBootPartitionTimeout /t REG_DWORD /d 30000
These commands allow some time for USB to be started so Windows doesn't go 7B.
I'm hoping my current test works, as I can use these micro images to be virus scanners. Plus if I work on getting VHD parent/child working, I would never have to redo the image as it would always be reversible.
If I could only get some of the more modern OS like 8 down in size like this one (still working on that) I could have a solution for UEFI. For now I use ODS for that (WinPE build) but it's quickly becoming more difficult to manage as changing tools requires a complete image overhaul, which even though can be scripted is tedious, plus each machine behaves different with PE, weird but true. With Thin PC all I have to do is boot the Master Reference Image, update the tools and image the DOM's (Disk On Module) fresh.
If you have access to VL Agreement Thin PC can help in more ways than you think.