[KoRn]

it's = its......(blushes)

[Cedar]

"I uncheck everything. Unless it's something you see in there you WANT running on startup.

it's = its......(blushes)"

You had it right the first time. It's means it is. So in your sentence that's what you were saying..."Unless it is something you see in there you want running.."

Its (with no apostrophe) is the possessive form, like..."The car ran great, until its timing belt broke."

Your first instincts were right!