Well, folks, after a couple of weeks trying (in vain) to safely delete over 1,000 files from system32 and syswow64, I have decided to proceed the other way round, by proceeding as follows:
1) copy ur vhd and make sure it is a working one, as u will need to alternatively boot off it many a time.
2) keep everything vital for u open and try to move all syswow64 dll's elsewhere; the reboot must be successful and everything that was open must work ok. if it is the case get rid of the dll's u have moved (u must be left with some 800 dlls in syswow64).
3) now get a bootlog and guarantee the presence of the following files
in order to boot successfully; place these files in a separate directory to be sure (the above files are necessary but obviously not sufficient for the system to boot ok).
Unlike the dlls in syswow64, which get blocked (undeletable) when ur favorite sofware is open, those in system32 don't tell u until ... u can't reboot, never mind get the software to work, so this is where ur vhd copy might have to come into play. So,
4) list the system32 root by type and concentrate on the dlls; select them, cut all deleteble ones and paste them to another directory, leaving alone those dlls that do not come off. the rebooting will not be successful, so
5) u will need to boot the copy and get the directory u have pasted the dlls to (now u can proceed by the criterion u see fit, me I prefer the alphabetical order, while others I know proceed by size - choose the criterion u can best manage, whereby u can keep track of all the files, as u have to do some trial and error). so, supposing u go by alphabetical order,
6) copy the dlls starting with an a and paste only the needed ones (2nd option on the copy box) back to the system32 root folder of the (obviously) offline vhd that had not booted before.
7) try to reboot and repeat the operations until u reach the bunch of dlls that will allow the system to boot (to cut a long story short, the system boots and works ok if the dlls with the following initials
A, bootvid.dll, C down to ci.dll, D (here I need some surgical integration to make my favorite software work, but you might as well not), F, kd.dll, L, M, Pshed,dll, T, W, X
are pasted back into the original root folder.
The above procedure leaves u with nearly 700 dlls deleted from system32 (and I believe some more can be deleted letter by letter, with a little more patience), plus 600 from syswow64 = nearly 1300 dlls deleted. ain't that something!?
8) once u r thru, keep a copy of the system32 and syswow64 root dlls elsewere to be sure to be able to resort to whenever needed.