One of the more common reasons for a failed MSE install is having had some other security software on the computer. Each security vendor usually provides their own official uninstall tool. Failure to use the tool can result in bits and pieces (remnants) being left behind which can interfere with a clean install of a new product. Singular Labs has compiled a list of official uninstallers. If you had a security product installed before MSE I'd run the appropriate uninstaller(s) after reading the info file(s).
Computer type Laptop System Manufacturer/Model Number Sony Vaio VPCEB47GM Laptop OS Win 7 Pro 64-bit CPU Intel i5 2.4 Ghz Memory 8GB DDR3 Graphics Card Intel HD 3000 Sound Card IDT High Definition Monitor(s) Displays 15.6 WGXA Anti-Glare LED Screen Resolution 1280x800
Hard Drives 640Gb 7200rpm Antivirus MSE Browser Opera (primary) with IE9 backup
Microsoft Security Essentials Error Code 0x80070643