Can older Bitcoin mining equipment be used efficiently on altcoins?

[Numbers]

Can older model mining equipment be used to mine any of the altcoins new or old? Would it be efficient/profitable to do so?

I am completely new to mining.

[ESJai]

ASIC? No. It can only mine what it was designed for.

[Vann]

You should be able to mine any coin that uses the same SHA-256d algorithm as BTC such as Namecoin or Peercoin.

[QuintLeo]

Only those coins that use the SHA256 algo can be mined by "Bitcoin mining equipment" - Namecoin is probably the best known of those, but *right now* DGB and Myriad (both of which can be mined using one of 5 different algos) are probably closer to being profitable.