Gateway windows 7

Greetings A friend of mine had to bury his son Had massive heart attack and died in there front room. awhile back Mom and Dad bought him a computer. Windows 7 they asked me how they can obtain password so they can use it. I told them to buy windows 7 cd and I would load it up. Problem is harddrive has 3 partitions. and when I try loading windows I can delete 2 but 3rd one whites out. Also do windows make the partitions? I used life guard tools It is a Tarabyte Western digital to write zero`s to drive but partitions are still there. When I selected to delete partitions and next page reads ( A problem has been detected and windows has been shut down to prevent damage to your computer) A driver has overrun a stack based buffer, this overrun could potentially allow a malicious user to gain control.of this machine
then there are, STOP: 0X000000F7 (0XFFFFF88002c12970,0X00002BF7E1316DBC,0XFFFFD4081ECE9243,,0X00000000000000 00)
I had reset bios and tried it but same result. When I had written zero`s it finished saying I had 1000gb.