First of all, right click on the taskbar > select properties in the context menu . In the resulting taskbar and startmenu properties window, there is a checkbox "use aero peek to preview the desktop" at the most bottom item. Make it sure that this button is checked, and post back .
Computer type PC/Desktop System Manufacturer/Model Number Self Assembled OS Windows 7 Home Premium 64 Bit SP 1 CPU Intel Core i3 2120 @ 3.30GHz Motherboard Gigabyte Technology Co., Ltd. H61M-DS2 DVI Memory Corsair 2GB x2 (Single-Channel DDR3 @ 665MHz) Graphics Card 2047MB GeForce GTS 450 (ZOTAC International) Sound Card Onboard (Realtek High Definition Audio) Monitor(s) Displays LG Flatron E2040T Screen Resolution 1600x900
Keyboard Logitech MK220 Mouse Logitech MK220 PSU uMAX 750 watt. Case iBall Cooling Air/ Fans Hard Drives Western Digital 1 TB
Seagate 500 GB Internet Speed BSNL Broadband Antivirus Microsoft Security Essentials Browser Waterfox Other Info Dell Studio 15" Laptop
Computer type PC/Desktop System Manufacturer/Model Number Self Assembled OS Windows 7 Home Premium 64 Bit SP 1 CPU Intel Core i3 2120 @ 3.30GHz Motherboard Gigabyte Technology Co., Ltd. H61M-DS2 DVI Memory Corsair 2GB x2 (Single-Channel DDR3 @ 665MHz) Graphics Card 2047MB GeForce GTS 450 (ZOTAC International) Sound Card Onboard (Realtek High Definition Audio) Monitor(s) Displays LG Flatron E2040T Screen Resolution 1600x900
Keyboard Logitech MK220 Mouse Logitech MK220 PSU uMAX 750 watt. Case iBall Cooling Air/ Fans Hard Drives Western Digital 1 TB
Seagate 500 GB Internet Speed BSNL Broadband Antivirus Microsoft Security Essentials Browser Waterfox Other Info Dell Studio 15" Laptop
Computer type PC/Desktop System Manufacturer/Model Number Self Assembled OS Windows 7 Home Premium 64 Bit SP 1 CPU Intel Core i3 2120 @ 3.30GHz Motherboard Gigabyte Technology Co., Ltd. H61M-DS2 DVI Memory Corsair 2GB x2 (Single-Channel DDR3 @ 665MHz) Graphics Card 2047MB GeForce GTS 450 (ZOTAC International) Sound Card Onboard (Realtek High Definition Audio) Monitor(s) Displays LG Flatron E2040T Screen Resolution 1600x900
Keyboard Logitech MK220 Mouse Logitech MK220 PSU uMAX 750 watt. Case iBall Cooling Air/ Fans Hard Drives Western Digital 1 TB
Seagate 500 GB Internet Speed BSNL Broadband Antivirus Microsoft Security Essentials Browser Waterfox Other Info Dell Studio 15" Laptop