Make and model number of the VGA splitter would help. If its what we suspect it is, it just sends the same source signal to two monitors at once. To extend your desktop across multiple monitors each monitor requires and independent video signal.
Computer type PC/Desktop System Manufacturer/Model Number Home Built OS Windows 7 Ultimate AMD64 CPU AMD Phenom II X4 980 Black Edition Deneb 3.7GHz Motherboard Asus M4N68T-M V2 µATX Motherboard Memory 8GB 4GBx2 Kingston PC10600 DDR3 1333 Memory Graphics Card BFG NVIDIA Geforce 220GT 1 Gig DDR2 PCIe Sound Card VIA VT1708s High Definition Audio 8-channel Onboard Monitor(s) Displays 2 x 19" I-INC AG191D TFT Flat Panel Screen Resolution 1280x1024 x 2
Keyboard Logitech Internet 600 Mouse Logitech Wireless Trackman Wheel PSU Retail Plus 465 Watt Case Power Up Black ATX Mid-Tower Case Cooling Stock heatsink and fan Hard Drives 500 Gig WesternDigital SATA-300 Drive Internet Speed 80 Mbps Down 30 Mbps Up Antivirus Microsoft Security Essentials Browser Internet Explorer 10 Other Info HP DVD1040e Lightscribe - External USB2