Trouble finding a rock band

[NRI_]

Hi! I know I'll be asking too much but I´ve been searching for a rock band for an entire week without luck. It must be from the 70s or 80s. The first letter is P and probably the second is o or r -- not quite sure. The band is known for making a cover in their first album as a requierement from the record company. Only then, they could record their album. The ironic part is that they are only famous because of this remake. Also, it is said that they didn't even practice the song. They just recorded the song in their first attempt. The cover they made was from an old band from the 60s or so.

I don't know if it is enough info. I really hope someone could help me.