Introduction and Q: Snape covers for Quirrell in PS/SS?

[bluebellblaze]

No: HPFGUIDX 33041

Hello, I'm new, and I'm a grownup HP fan. :-)

I have to say I only discovered HP books after going to see the movie 
with a nephew and absolutely loving it. I read straight through the 
four books in the next couple weeks. Anyway, I've been reading this 
group for a few days and have checked through many many of the past 
messages and have read through the VFAQ. Forgive me if this has been 
discussed endlessly already. If it has, just let me know and i'll try 
to search out the relevant posts, but here goes:

Is Snape a vampire? kidding!!!!  ;-) My real question:

In SS/PS, Snape suspects Quirrell is after the stone and confronts 
him privately, but he does not go to Dumbledore with his suspicions. 
I know there is one theory that holds that Snape is doing his own 
detective work against Q, so he can eventually bust him single-
handedly and take the credit all for himself, once he's got enough 
evidence. But what i get from reading the scene in that Snape is 
actually warning Q, as if he <gasp> cares about his DADA rival (you 
better decide where your loyalties lie....), as if he is trying to 
warn him off doing whatever he's planning. But why? Could they have 
some sort of past together? Could Q have been a former DE like Snape, 
and Snape is sincerely trying to save him from turning back to the 
Dark Side? I"ve (only) read the books once each, so maybe i missed 
some tidbits of info that shed light on Quirrell's pre-Hogwarts life?

mary