Change of account, but it's still me. (I couldn't see any way of renaming my account.)
Yes, it is. Please describe what happens durung boot. What's the failure?
What is common inside the "non booting" machine, and different from the "booting" machines?
The problem which ALWAYS occurs for me with WinBuilder2015 is that "easyDriveLetter" window appears, saying "The number of drives with the multiPEBoot signature is 0". It then lists various partitions, sometimes including the one it should use (which is "X: Boot"). Unfortunately the keyboard never works, so I'm unable to get any further than that.
I've also seen this issue with EzPE3, but (seemingly) it's not so common, and (I noticed recently) if I wait long enough then the keyboard *eventually* starts working (at least sometimes) so that I'm able to enter a drive letter & get it to boot. (I suspect that USB hubs make things worse, but sometimes they are built-in to the keyboard/mouse combo, or even the computer itself.)
I've never had any "easyDriveLetter" problems with other bootable CDs, so my personal feeling is that "easyDriveLetter" should probably just be scrapped in favour of whatever other PE disks use. Or at least if "easyDriveLetter" fails, then it should fall-back on whatever mechanism other PE disks use.
Unfortunately I don't have a record of which PCs had problems, and I cannot check them again (one-off visits). However, my own PC does have this problem, so easy to test.