Recently, a friend gave me a 8310 to help fix but I am clueless as to how to approach it.

Basically, when I put in a battery, as all BBs do, it turns on automatically but the system never comes up and all I'm able to see if a slow blinking red LED. I plug it into the computer thinking that I might be able to use jl_cmdr to try to reset the system and put on a new OS but my computer doesn't even recognise or pick up the blackberry. I have attempted this on a vista machine as well as an xp machine. Anybody have an idea whether this BB can be rescued? Thanks in advance!

UPDATE: Actually, the sequence of LED blinks is, slow, fast, fast, fast. And that's the pattern that repeats.

I would try following these steps:
What to do next if Jl Cmder will not connect and wipe - BlackBerryFAQ

Take your time and be patient as it may take a multiple attempts for the device to be recognized.

thanks for the link, unfortunately, I tried several times but simply couldn't get the USB:UNKNOWN or USB:BBPIN to show up. I tried to plug it in right when the first LED blink starts and also during the sequence of three fast blinks but still no go. Only ever see COM1 and COM2.