Alienware x51 andromeda r5 - lot of issues

Hello comunity,

recently comes to my hands above mentioned machine (not custom, all factory build) from my brother, since he hardly use it at all since he bought it (may 2012). And she has a lot of issues i cannot resolve:

1. She crashes. If put under any stress (start a game, running a test, basicaly anything needing more processing) it crashes immediately without warning. During this i tryied SpeedFan app but it dont show any excessive temperature on cpu or gpu. And she crashes so hard i have to unplugg power cord for a few seconds to get her run again.

2. Problems with connection. Uses Dell 1502 wireless adapter which has connectivity issues: disconnects all the time, than fail to reconnect for a long time showing limited access or no network at all. And when it finally connect to network signal strenght is below average altough other devices around has strong signal indicating. Have been trying to resolve it by advices found on forums (reinstal driver, turning preamble on long on router, switching buffers setting, power options and others) but nothing helped

3. Jet-plane sound of vent (2 i think) placed on front, going almost non-stop even when temperatures are okay. 

4. During booting "power sensor failure" message appearing

5. After win7 is loaded command centre always ask me to permission to make change on hard drive (system message) with no detail just CLSID : {0DBCA9B6-3003-4229-B78D-DD6800FE06E8} and obviosly i have no idea what is it doing and how to fix this. 

Is anyone able to help me with any of these? Preferably no.1 and 2 because they are really pain in my back door.