it is a post chosen fic
I just remember the begining: Buffy came back to college and on her first day met her new english professor : spike
spike don't remember anything of his past

I remember this fic but it's name escapes me right now. It's spuffy, not Spike/Dawn.

yes it's definately spuffy
sorry I read this fic a long time ago and I don't remember any details

This one is similar to it but it's not the one I am thinking of. Just in case it is the one you are looking for I'll include it here though.

You Don't Know Me by Sophie

http://spikeluver.com/SpuffyRealm/viewstory.php?sid=1763

Summary: After the collapse of Sunnydale, Buffy and the gang rebuild their lives in L.A (with a little help from Angel). They are not the only ones...

In this one Dawn sees him first and he is working at the library. In the one I am thinking of Buffy finds him as a professor and Spike not only doesn't remember her he doesn't seem to be interested in her either and she has to really work at getting through to him and getting to know him again. Still searching for that one...

it is not you don't know me
but for the other I think it really could be the one because I really like when it's Buffy who goes after Spike

Could it be Sweet Lethe by Miss Murchison?
Buffy runs into Spike at the Hyperion post-Chosen, and he's human and doesn't remember anything about his past. There's a sequel - Forget and Smile - where Spike is a teacher at a school Willow is running for Slayers/witches.

Well... never mind. This isn't Buffy going back to college. Still good stories, though.

I may be mixing up fics, but wasn't it kind of like a take on 'Spotless Mind' where Spike purposely chose to not remember in order to make it easier when he was brought back as a human after his 'death'? So he really didn't remember Buffy because he had planned it that way? Or was that a different story? If it's the same story perhaps this will jog someone's memory about an author or name of the fic. I know I read it but I just can't recall the name of it. Dang.

Could it be [i]My Life Closed Twice[i] by Anaross? It can be found at the Just Rewards website. Spike is a poetry teacher at a university where Buffy finds him. She audits his class but he seems to want nothing to do with her. It's post-series.

No, it can't be My Life Closed Twice because in My Life Spike didn't lose his memory he just didn't want Buffy in his life when he came back. And she didn't discover him as a student, she found him and then to pursue him audited his class.

No, the one I think we're looking for is when Buffy found him accidentally and he has no idea who she is. And I think it is possible that Giles had helped Spike obtain the memory erase...If it's the same story. So frustrating!

So frustrating indeed!
Now I begin to think that when I read this fic it was still a WIP and the more details you tell Smac the more I want to read it again