The PG48 is a "high impedance" (Hi-Z) mic, designed to be used with a 1/4" plug at the end. The SM57 is a professional mic, designed to terminate into a Lo-Z, 3-pin XLR input. You need a transformer plug that will electrically and physically adapt an XLR cable(you'll need that, too) to your 1/4" input on your soundcard. Check with a local Radio Shack (at least) or a decent music store. They should be able to hook you up (bad pun!)...

it could also be that your mic is broken but i'll doubt that. you need to unbalance it and add some gain. don't drop it .

I don't know what you mean your "computer doesn't recognize the microphone"??? Computers don't "recognize" microphones. Microphones are not computer "devices" - UNLESS it's a USB microphone!(Which neither model is - the PG48 is, pretty much, just a "school cafeteria version" of the SM58.). With an ordinary computer soundcard, you plug the(Dynamic, which both are, or maybe an "electret condenser", which often run on internal batteries and neither of yours are.) mic into the mic input of the soundcard, using the proper adapter - in your case, for either mic, an XLR female to whatever your soundcard mic input is(1/8" - 1/4"?), and it just works, with your software - no other power supplies or preamps neccessary(Though a nice pre could be helpful?). Due to differences in impedence and sensitivity one or the other mic may need to be "turned up or turned down", respectively, using your audio software or Windows Mixer OR here is where that "helpful, external, mic preamp" might help, but, far as it goes - it just works.

Why doesn't your SM57 work?

Possibly broken? If you bought it from "some place"(Not a reputable dealer) on EBay, it may be broken... Even if FROM a good person or dealer, some things DO just get broken? If you find it IS broken, give the EBay person a chance to "make it good".

If your PG48 works with the computer and the mic cable you have, the SM57 should work - again, at least to some, similar degree(Though the 57 should sound "better", as it cost 3x more, originally)...

You could go to the Shure web site(As I did) and download the .pdf,files for each mic and make sure the cable wiring(Called "pinout") is the same for both mics, just to be Shure(I didn't compare)?

You could try the SM57, on another computer or amplifier, mixer, etc., almost anything with a mic input?

Lastly, speaking of mic input, 9 times out of 10, when someone with a "normal" computer has this problem(Mic doesn't work), they have the mic plugged into the "line input" on the soundcard. It MUST be plugged into the "mic input". Take a look and make Shure...

TG