W7 Sharing & Security Questions

First let me say that I posted a very similar inquiry to a forum of a different group using a very Milquestoastian name and got no replies, so I come to this forum as BizarroMindMelt to see if my luck improves.

BACKGROUND: Very small office will replace 3 XP32 systems with 3 new Windows 7 Pro 64-bit systems. New master Windows 7 system is loaded with all s/w; boots from C: and has X: and Z: on second drive.
(Intention is to clone the master to the 3 replacement systems, adjust licenses, and to set new PCs to share X: from the master (which will be pretty much reserved as a share-source) and use the space which would have been X: on each station instead as Y: for backups.)

PROBLEM: Vendor remoted in to install odd proprietary s/w on X: on the Windows 7 master, and tried – too hard! - to make it sharable to the 3 existing XP systems, just as it must be to their replacement Windows 7 systems. He was not successful, but in attempting to get the XPs access to the shared Windows 7 files, I now see that he has very efficiently set what will be our clone-source to look like Swiss cheese: EVERY possible setting is wide open. Root is full control to you readers and anyone. Settings for “Present bank account data to Chinese hackers?” are now checked “Yes, gift-wrap please.” (I do not believe he made any manual registry changes, at least.)

I am no longer concerned about XP access to the Windows 7 partition share because I will be replacing the XP systems entirely in days with the Windows 7 stations I will clone.
I am computer literate but not expert in Windows configuration, and this is my first Windows 7 attempt.
Because so much odd software has been loaded by vendors I cannot readily start over with the master Windows 7 system. I seek help with two matters.

PRIMARY QUESTION: facing such a situation, is there a simple guide (or program!) to reset Windows 7 Pro master to reasonable security consistent with second question?
Or can someone offer/link a short list of settings including well-hidden ones? (Very well hidden ones all appear to have been changed!)

SECOND QUESTION: plan will be: clone Windows 7 master to 3 workstations; change license keys as appropriate and set stations to access partition X: from the shared master, which will then be generally dedicated for sourcing this shared resource. (All stations will have own s/w except the odd s/w meant for such shared use.) I have not yet studied setting up Windows 7 to share a full partition in homogeneous Windows 7 LAN but assume will not be very hard to configure. Just need the 3 stations to have r/w or full access to X: on the master.
Has anyone any favorite cautions or tips on easiest way to do this beyond those easily found in other threads?

SYSTEM: All W7 PCs are identical homebrew using AMD 640 CPUs; network uses BEFSX41 router to DSL modem; plan to replace router with entry SonicWall TZ box soon (if I can afford subscription; got box free). Initially will use MS free security software on each system. Expect to begin use of cheap cloud storage such as SugarSync in some months.

BizarroMindMelt thanks you for any assistance... SHAZAM!

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