Thank you, yancek, for a very comprehensive reply. I have read up on GRUB until I was totally frustrated, and I finally tried one of the simple install command lines. It said it worked, but later I found that the graphics and the disk info had not been registered along with the Stage1 loader. Fail.
I'm certain someone competent could have surgically corrected the problem within five minutes. I opted to reinstall PCLinux, losing a couple of hours of setup time I had invested. So it goes.
On the Windows side, the Win7 Recovery Disk routines did nothing for the MBR, which is exceedingly lame, but I found the console command to use. For subsequent viewers here, it's
bootsect /nt60 c: /mbr
where C is the drive with the mbr in need of repair, and it works effortlessly.
Perhaps you're correct about a minimal amount of reading being able to prevent this mess, but
a) I think a minimal amount of contextual help during the installation would be most appropriate; there was none. A simple paragraph concerning file location ramifications to a multiboot situation would have been most welcome. As it was, merely cancelling out of a sub-dialog caused the entire GRUB routine to terminate on my first time through, and I had no idea for a while if anything I had done had succeeded.
b) the subsequent GRUB reading I have done only took me deeper into the abyss of a problem I knew had to be simple at its core. I frankly feel that a lot more can be done to make this system user-friendly to newbies and those not super technically adept; and that doing so would increase Linux's appeal exponentially.
Thanks again for your conceptual help on this. It gave me the overview to see where I needed to go. Much appreciated.