Your out of luck
Q3: Is Intel providing WDDM drivers for Intel Graphics Media Accelerator 900 (Intel GMA 900) on Intel 915 Express chipset-based platforms?
A: Intel will provide support for WDDM drivers beginning with the Intel® 945 Express chipset family and beyond. See question 5 below for a detailed explanation of WDDM support on Intel® 915 Express chipset-based platforms.
However, Windows Vista is supported on the Intel® 845G, 865G, 915G Express desktop chipsets and 852/855GM mobile chipsets running XPDM (XP Display Driver Model) drivers for Intel graphics. Windows Vista will install on these platforms, but advanced features such as Windows Aero will not be enabled as XPDM drivers do not support Windows AERO.