Definitely logged in as admin. If you are not an admin, you can't even access the registry!
Open a My Computer windows. Click View, folder options, file types.
Scoll down to the php row. Select php, click delete.
Try associating again.
3.06GHZ 524 HT EM64T 533 MHz,
1024 MB RAM PC4200 DDR2,
160GB 7200RPM HDD,
Nvidia Geforce 6200SE TC 256MB,
Sound Blaster Live! 5.1,
Logitech G15 keyboard,
Razer Diamondback mouse,
Windows XP Home SP2,
OpenSuse 10.2