My 360 had recently crashed with the E74 error message... it turns out its the GPU so what i did was... the X-clamp mod :D worked like a charm, and im back gaming again!
Here is a walkthrough that my dad found. this works a treat :D
http://www.mediafire.com/file/nmnzlmcyz0x/FIX FOR THE 3RLOD.doc
The blog of a Australian Gamer.