op, and older HP DESKTOP only 0 years old today 2011 your question lacks a question. the word hOW TO , too hard to type? IDK, only can I guess you r meanings. the answer is simple. power cord pulled from wall. AC wall jack. 1: mount the new drive in the HDD cage in side. 2:plug in HDD power cable from PSU. 3: plug in HDD SATA cable from SATA port to HDD. 4: power on PC, and in disk manager assign it a drive letter and format it. bingo works now. that simple, the service manual stinks, looks link no drive bay HDD2, there. looks like no extra power cables for 2nd HDD, if you have no need for DVD , use those 2 cables will work, and if a SSD recommended, just tie warp the SDD to the case bar just above the existing HDD. there are no IDE PATA Drives, here per Andrew.HP does show w10.64bit support, wises.this PC is 100% SATA drive PC, ! not year 2000- IDE.