On Windows 7, from the experience of test installs, you set up the administrator information during the setup process. It's when you enter your Admin Username, I don't see how you could have missed that.
But there is always "Account Control" in the Control Panel.
Computer type PC/Desktop System Manufacturer/Model Number CYBERPOWER OS Windows 7 Home Premium 64-bit SP1 CPU AMD Athlon II x2 260 (3.20Ghz) Regor 35nm Technology Motherboard ASUSTek M4N68T-M-V2 (AM3 Socket) Memory 4GB Dual-Channel DDR3 @669Mhz (9-9-9-24) Graphics Card Zotac GeForce GTS 450 (1GB) Sound Card Nvidia High Defenition Audio Monitor(s) Displays Acer S231HLbid LED Monitor 23" Screen Resolution 1920x1080 1080p 60Hz
Keyboard XTREME Gear USB Keyboard Mouse XTREME Gear USB Mouse PSU SeaSonic M12II 620 Bronze Modular Active PFC 80+ Bronze Cert Case Cooler Master Elite Gaming Case Black 430 Cooling Cooler Master Hyper 212 Heatsink. Front and rear 120mm fan Hard Drives 977GB Hitachi HDS721010CLA (SATA) @7200RPM;
488GB Western Digital WD5000AAKB-00H8A0 (PATA) @7200RPM Internet Speed 300Mbps Belkin Surf/Share Wireless Browser FireFox/PaleMoon Other Info Windows installation was of June/July 2011 to my knowledge.
It should ask for your User Name then a password if you want one. The account setup during install is assumed to be owner's account so it is a quasi-Administrator but not the hidden Administrator which has to be enabled from hiding.