Idiot Computer Question

[Rutskarn]

I'm 99% sure the answer is, "no," but I'm just checking, here. Is there any way you can easily convert a microphone jack into a headphone jack on a Dell Vostro 1510 laptop? Like, without cracking the case open.

I know, input, output, etc, but I was wondering if I was missing something.

[Jack Squat]

Without cracking open the case, no. Simple answer is because no matter what you plug in, it's going to register it as a microphone.

[Reinboom]

There is a possibility of converting it without cracking the case, yes. However, you would, at best, get a mono line.
You would need, at least, some degree of software familiarity as well as the likelihood that you will need to write a new 'fake' driver for the soundcard, requiring rather low level (where low level usually equates to 'more difficult', though not absolutely) programming experience. :edit: Extension: you may even have to flash new firmware, depending on the card. All in all... risky. I would not recommend attempting unless you are willing to throw away your sound card altogether.

The sound card must differentiate the difference between the microphone-in and output on a software level. Or, must be able to feed static.

In most cases, you will most likely need a direct box.

tl;dr
Possible? 'Maybe'. Easy? No.