Painting - Peeling Paint

I recently purchased a co-op that needs to be painted. While patching old nail holes, i came across a crack in the paint on one of the walls. It was a bubble and I used a scraper and started scraping away the paint. To my surprise, the paint came right off. My problem now is that i scraped off all that would come off, about a 5 foot high and 1 foot wide patch. There were so many coats of paint from previous owners that now the wall is uneven. My question now is this: do i try put a thin layer of putty and sand it down to even it or do i just sand down the old paint to make it even, or do i find a way to remove all the paint from the wall? Please help. i need to move in soon!

You can easily do your job in one application using the PEEL AWAY 7 paint remover. It is available at Sherwin Williams paint stores.