My car is screwed! Help me, please!?

My car was making a scretching noise for three weeks and the battery was draining one day until it just completely died and wouldnt click over or nothing. DEAD. Its been jumped but once you let off the jumper cables and get ready to shift into first gear it completely dies and wont click back over. Well its just about sat out for 2/3 months. My two guy friends (one working at VIP) have replaced the alternator and replaced a new battery, now it kicks on when you jump it and runs for like 5 minutes tops then will completely die. If you let is sit out long enough like over night the next morning it will start on its own but it will evenually die in 5 minutes. All fluids are checked, the old alternator and new alternator passed at Advanced auto parts, so thinking it wasnt an alternator issue... now.... Me being an asian chick that dont speak car language I HAVE NO CLUE WHAT ELSE THERE IS TO DO! I have a 92 SAAB 900 Standard 4 dr Sadan. Now is it a wiring issue or what Guys? I just want advice and rough estimate this type of work would cost. I love my tanker car and want whats best for her. Please help me out.