2002 Electrical Issue

I was putting in my amplifier in my trunk and as i put the ground to the amp terminal i lost all power throughout the car. I dont know what it could have been and it hasn't been the first time i put a system in a car.I checked the battery and tryed to jump start it but nothing, i also tryed to use a BoosterPak and still nothing. And, inside when the battery was hooked up the "CHECK ENGINE" light woudl only come on in the bottom right hand corner of the guage cluster. So does anyone have any idea as to what it could be? I need to get this fixed ASAP and hopfully it's a small issue that wont cost very much.

Any and all help is appreciated.

maybe you should buy a compassitor for your auto system ..or maybe your battery is'nt good enough ... I just installed eight speaker DTS HD dual din radio system n my 2001 impala.... i had to deal with some issues ..with installing a aftermarket radio in my impala.....the dealer told me that I will lose my" Door chimes" Oil reset ," Low tire pressure" reset and "fob light and fob horn options that only could be done though the the factory radio ... Unless i get metra VT-GMOS -04 adapter ....which cost me 100.00 bucks and it works great !........

check the underhood fuse and relay center for a blown main fuse.

Sorry to say but the problem has been fixed , was fixed the night i posted it realized that i blew the fuse for my system and didn't hear it pop so... But thanks for the help, and i dont run with a capasitor i have another battery in the trunk =) befor i had 3.

Thanks for the help