[Fezzik]

It can mean I had, I would, or I should, depending on context:

http://www.merriam-webster.com/dictionary/i'd

[taneq]

Wow, that's crazy and ambiguous. I've never heard of "I'd" as a contraction for "I should", how do you tell whether to expand it as that or "I would"?

[ktRolster]

I think it's archaic,

"I should think so"

[startling]

Context.