hey, brink, thanks!
unfortunately, step 6 says:
6. To Enable System Restore -
A) Check the
Available Disk letter(s) that you want System Restore to create restore points for and stored on the same drive. (See screenshot below)
NOTE: Each drive selected will have it's own restore points stored on only that same drive. For example, C will not be stored on D, and D will not be store on C.
[orange emphasis added]
the note says i can't do what i'm asking, that C: shadow copies are ALWAYS kept on c: in fact, i believe it makes much more sense to store them on a different disk. and ms has system commands that do that. remember:
cmd>
vssadmin add shadowstorage /for=c: /on=t: /maxsize=10gb
why two different parameters (on and for) if they're always the same value?
am i more clear now? i want to store the shadow copies from my system and boot disk c: to another disk t:. that way i won't get all the failures i'm getting now, vss memory allocation will work, and it won't compete with system and applications pounding on c:. it's actually the advice given in the error message. one hand says do it. the other hand takes it away so you can't. :|
btw, same thing applies to placing the pagefile (vm swap space) to a different (preferably, fastest) disk. then the disk arm is freed from the fight, where vm pulls it to the pagefile, and then application pulls it to its files...then back and forth. it's called thrashing. i'm glad to add that this is in fact do-able. system control panel, advanced tab, performance button, advanced tab of that, button change... and then you can specify the location, name, and size. that's what i want for vss.

ooops. i made the same mistake brink did. when i read that change... dialogue (for the pagefile) it seems it actually lets me change only size. not which volume. ok, i want that, too, if anyone knows how? lol