Hi
That is a typical sign of power supply problems .. not necessarily HDD failure. You need to get a replacement power supply kit and install it .. or send it off . or get sky to replace the box ... at a price.
The kit is upgraded with better components. 2-3 years average life for HD Thomson & older boxes. Some reputedly better than others .. like Pace.
Have a look here if Thomson .. kit is easy to install tho.
http://www.satcure.co.uk/tech/thom_psu.htm
Fan controller can also be a problem ..
http://skyplusfancontroller.com/hd.aspx
More stuff here ..
http://www.digitalspy...owthread.php?t=801698
Answer to last one ...Yes. No more than 110 quid tho. They usually do exchange tho for less money.