Interface wont work with microphone

you need a recording interface (with phantom power if the mic requires that - most condensor mics need phantom power) to go from the mic to the interface, then to the computer. There are many USB recording interfaces - some easy plug and play interfaces include:

http://www.amazon.com/ART-Project-Series-Microphone-Preamp/dp/B000K6B59Y/ref=sr_1_8?ie=UTF8&qid=1334413603&sr=8-8

Then on your computer you need an application such as audacity (if windows), cubase, sonar, logic, pro tools, or any other audio recording app that will allow you to record and edit tracks. From there, you can install many different plugins or apps that can process the audio and add effects to the tracks like reverb, delay, distortion, etc.

Was it working fine before it stopped powering up? The U87 is a condenser microphone so maybe the reason it is not powering up is because the phantom power on your interface was not turned on. Plug the U87 into your preamp and then switch on the phantom power (48V) to get it powered up. If that doesn't help, there must be an internal fault within the microphone or in your preamp.

you just need a cable.

you should be using these:

M-AUDIO - Fast Track Pro - 4 x 4 Mobile USB Audio/MIDI Interface

This mic has a 10db pad or attenuator switch at the base of the barrel maybe you clicked it on by mistake,
Try changing the lead.
The power supply on you preamp may be failing or had the voltage selector also clicked to the wrong setting.
These are cheap things to try before spending money.

This mic has a 10db pad or attenuator switch near the bottom of the barrel... make sure you haven't accidentally engaged it.

If that's not.... it try changing the lead. Also the power supply on your preamp could be failing.
These are a few cheap things to try before spending money for fixing.

You'll need an interface or a mixer.

If you are refering to the softwar Mixcraft, then yes. Combined with a suitible Mixer or Preamp connected to your computer's sound card, or an External Audio Interface with build in Preamp, you will be able to record with the NT1-A.

Your Mixer/Preamp/Interface needs to be capable of providing the mic with Phantom power to operate.

Is It A Condenser Mic? If So You'll Need Phantom Power

When you are installing the skype software, there comes a time when skype will offer you the option to test your hardware. Here you will try out the speakers and mic, and skype will tell you if they are in skype accepted order.
My friend actually installed it not too long ago, and after the install, I saw that skype gave him the option to make a test call right on the program interface window. We used it, and it made a call to a skype computer voice which advised us that if we could hear her talking, then our speakers are fine, and to now go ahead and speak into our mic, if the mic is working we will be able to hear what we just said into it.
That was a great little way to make sure our speakers and mic were in fact working, and they were.
Try that out on your pc and your friend's pc to test components individually. If you are unable to find the test call option, or the option to test components, you can uninstall skype and reinstall the latest version, which may not be a bad idea to preclude any other weird problems which may be at fault.
Hope that helps.