Fortune left West Brom for Celtic in the summer of 2009 before rejoining to the Hawthorns last month in a surprise move.
The 29-year-old claims he has no regrets about leaving West Brom for Celtic last summer, but is relishing his return to the Baggies.
"I'm a footballer, I like a challenge and went to Celtic. But I never regretted it," Fortune told the Birmingham Mail. "Celtic were a big club and I played well up there, though I'm glad to come to West Brom.
"It's good to be back. I had a good time here, with some good memories."