I recently picked up a 2006 MacBook that had been upgraded with "Snow Leopard OS X 10.6.8. There are many problems in trying to establish a firm foundation. Some of my Fourm Threads have advised I reinstall the OS. Today I purchased Snow Leopard OS X 10.6.8 from the Mac Store. My question is: should I refurbish the HD prior to installation ? or just reinstall it.