Hello, I own a Macbook Pro 13" (mid-2009) and about 50% of the time it will freeze on boot-up (startup) on the apple logo / small revolving circle. This began happening on the Leopard OS, I chose to do a clean install to Mountain Lion after erasing the HDD and the problem has continued to occur. The Macbook Pro does not recognise its disc drive (it does not appear in the system profiler) and is completely unresponsive. I have also had trouble in the past with the airport card not being recognised but this strangely resolved itself. I am wondering whether these hardware issues may be the cause. Any help would be much appreciated. Thanks.