I have one red light

It could be a few things. I would recommend calling Microsoft Tech Support on this one. Some causes of this error code are:

Section 4 is flashing red
- Hardware Failure
/ \
\ /

The Specific Type of hardware failure can be determined by the error code displayed on the screen.
If the screen is blank or you would like additional information follow the instructions for determining the secondary error code in the section below
E45: Unknown (possibly dashboard update related)

E64: DVD Drive Error.... DVD Timeout, Wrong firmware, dvd is without f/w chip, etc.

E65: DVD Drive Error.... DVD Timeout, Wrong firmware, dvd is without f/w chip, etc. This can also be caused by the tray not being fully closed on boot.

E66: DVD Drive Error: DVD model, or version does not match that of the version expected by the dashboard. OR the firmware version on the drive is older then the firmware version expected by the dashboard. Make sure the DVD drive is of the same version originally included with the console and that it is using either the original firmware included with the console or newer.

E67: Hard Drive Error... It 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 without it

E68: Voltage Error... This error means that the Xbox 360 has insufficent power to function properly. This can be caused by an error in the hard drive or the fans that make them suck up too much power, it can also be caused if you have unnecessary accessories attached to the console like an external fan unit. Attempt to remove unnecessary accessories first, and then necessary components such as the hard drive and USB devices. If you have any case mods you may want to investigate those as well.

E69: Hard Drive Error... It 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 without it

E71: possibly a dashboard update error, Check below in the "Console Reset Codes" for instructions. If that does not work there is no other solution and the console must be sent back to MS for repair.

E72: (not yet known)

E73: General Hardware Error: Ethernet port... this error is caused by a problem with the Ethernet port.

E74: There is high chance it's a scaler chip problem (the "ANA" or "HANA" chip near the AV cable connection) it can also be caused by a faulty AV cable so check that first. In some cases it is a problem with the GPU and may be repairable by doing the x-clamp replacement (see error 0102)

E76: This error deals with the Ethernet port's controller chip, a dead chip may not cause the error but removing the Ethernet controller chip does, it may also be caused by other Ethernet related problems.

E79: Hard Drive Error... It 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 without it.
According to tmbinc: E79 is the error code if xam.xex could not be started, i.e. probably a file system corruption.

The cause of E-74 with one red light problem might be overheating of your console and for avoiding such error in future you need to put your machine at an open space. Ensure that it is placed near the window or you can also make some external arrangement for cooling of console such as cooling the machine through a pedestal fan.
But as your Xbox already have E74 with one red light Problem which can be solved by only repairing it, no other alternative.
Either you can send your Xbox to Microsoft (Please note that microsoft is no longer providing extended warranty for E74 with one red light Error) and wait for 3-4 weeks. If you don't want to wait for a month, you can also fix E74 with one red light problem with the help of this DIY Video, the guide will explain step by step approach to fix the problem. Choice is yours.