Can you press and hold down the power and menu button on the front for 15 seconds, What should happen is that the phone will turn off then back on then turn off a second time.
When it ges off the second time can you then try waiting 5 seconds then press and hold the power button for 2 seconds and see if it will respond correctly.
If not can you press and hold the power and menu again for the 15 seconds then connect it to your computer and open iTunes and let me know if it is detected.
If it is you should have the option to restore the phone, say yes and the copy of iTunes on your machine will reload the phone with the latest version of the iPhone software then after it restarts it will restore all your files etc back to the phone.
Let me know if you have any issues.
Can you tell me if the phone worked correctly after he ran Blackrain?
Can you try pressing and holding hte power and menu keys for the 15 seconds again then when it turns off can you press and hold the menu button down and power up the phone and keep the Menu button pressed for 30 seconds and then try to connect it to your computer and see if the phone is then recognised in Disk Mode.
Let me know
Do you have applecare on the phone as I am sorry to say but it sounds like your friend managed to Brick the phone in which case the only thing you can do is take it back toan Apple store and have the phone swapped for an new one.
Let me know if you need more info
when you plug the phone into your machine do you hear the USB connection chime?
To jailbreak a phone is to take it out of Bellsouth and apples control so that you can then load any music, ringtones, or content you want as well as making it possible to use the phone with a different cellular network using a sim chip from another phone.
A jailbroken phone can work with any carrier that offers 3G or GSM service so that you caould use someone like crickets 3G service and have a working iPhone for $30.00 per month
This Wiki article will explain what it is all about http://en.wikipedia.org/wiki/Jailbreak_(iPhone_OS)
The problem is that if the Jailbreak is done wrongly you can end up causing major damage to the hardware so that you end up with a Bricked phone like yours which by the soundds of things will not even respond to the USB connector.
Honestly at the point you can try is leaving the phone disconnected for about 5-7 days till the battery dies and see if you can then get a response by plugging into your machine or you will have to get your former friend to replace the phone for you.
Everything we have tried is all we can do and if it wont even respond to the USB there is nothing more that can be done.
More than welcome.
Sorry we were unable to help you get it all sorted out.
I am sorry but I need to have the last word so that this question is removed from the top of my open question list telling me that you are waiting for me to respond.