So you are experiencing problems with your Xbox 360.
Well, you certainly are not alone.
Here is the top five list of Xbox 360 glitches, probable causes and some possible solutions:

1. General Hardware Failure E73 - 3 Red lights or the Red Ring of Death.
   This Xbox 360 problem can have multiple causes.
   The biggest suspected culprit is a short or bad cold solder joint associated with the RAM, CPU and GPU chips.
   Another problem that makes this problem worse is the excessive heat build up.
   So these two problems are really interconnected.
   The bad solder joints combined with the overheating/cool down stress, weaken and possibly cause the solder connections to break.
   There are a couple of solutions that are commonly used.
   The first deals with the "X" clamps that hold down the CPU and GPU chips.
   The second deals with over heating the console and basically trying to re-solder the broken chip pins.
   Do not attempt either of these fixes if your Xbox 360 is under warranty.
   Send it in and let them fix or replace the unit.
   
2. AV Cable Error E74 - This problem really couldn't be any simpler.
   Basically, here is a problem with the AV cable, so try a different AV cable.
   If that doesn't work there could also be a problem with the encoder chip.
   If the cable was working then there is a 90% chance it's a scaler chip problem (the "ANA" or "HANA" chip which is connected directly to the AV cable).
   In rare cases it is the GPU (refer to problem 1).
   
3. DVD Drive Error E64 to E66  - Again a very simple problem and fix.
   The drive is not connected so connect the DVD drive to the boot.
   
4. Hard Drive Error E67 to E69 & E79  - This could be a problem with the Hard Drive itself or a problem with the internal connection to the hard drive.
   Try removing the hard drive and playing the console without it.
   This problem can also be caused by a corrupt or missing eProm.
   
5. Power Supply  - This could be the PSU and could also be the GPU/CPU.
   One way or another the console isn't getting clean power from the power supply.
   You may need to get another power brick.
   

In the end all of these Xbox 360 problems can be easily fixed with a little internet research.
There are plenty of guides available which cover these Xbox 360 problems and more.
Make sure you do a comparison of any repair guides before making a purchase.
Good luck and good gaming.