I switched to WinPE 3.0 in the hopes that I could tweak it enough to get around this problem and I did. Here are the stats:
File system size: 45MB (uncompressed)
File count: 140
Registry size: 1.29Mb
Supported peripherals: SATA and IDE drives, Keyboards
RAM usage: 111MB (without pagefile)
Sooner or later I'll slim the registry down some more to get it below 1MB. Also, the file count and size could be much smaller if I kicked out all additional ide-drivers. Since I only need this environment to run a batch-file, I could even get rid of cmd.exe (including its dependencies). This would lower the file count by 15 files and the final size by may be 1.5MB. However, I left it in for the sake of usability.
I'm pretty much satisfied with what I achieved. There are only two things that I would want to improve:
1. While I was able to get rid of some security features, I wasn't able to remove the cryptography functionality. This makes up for 2.5MB alone and who knows how much RAM. I was able to remove it to a point where the boot process didn't BSOD, but only sat there, just before calling conhost.exe. So I guess I overlooked some registry entries or something.
2. PE 3.0 still caches files (or does something else that eats more RAM than it actually needs). So in order to get rid of this excess buffering, I use 7z to clear out the memory. Usually, I'd use a memory cleaner, but I couldn't find one that was both command line only and supported x64. The more elegant way of course would be to disable PE's RAM-eating behavior directly, but I couldn't find an option. I'm not even sure what exactly is going on. Still, I'm glad I found a way around this issue.
Here's a screenshot of MicroPE x64 in action:
![Posted Image](http://img684.imageshack.us/img684/3449/micrope.jpg)
Download MicroPE x64 1.0