Did you try to install Oracle using the Compatibility mode? Go to the properties page of the Oracle installation program (right click the icon and select Compatibility). Set for XP compatibility and also check the Run as Administrator. After installation, set the same properties in the Compatibility Tab for the program icon. Many people try this for just the program icon, but you need to do it for the installation program also for some programs. I have been successful with every "old" program that I have tried.

XPS M1530, Vista Home Premium SP1, T7250 Core 2 Duo (2.0 GHz 800 MHz FSB), 4 GB DDR2 667 MHz RAM, 200 GB SATA II 7200 RPM, Nvidia 8600M GT 256 MB - 156.63 Driver, Wireless-AGN Mini-Card, BlueTooth, WSXGA+ High Def LCD (1680x1050) w/ 2 MP Camera

Dimension 9100, Dual-Boot Win XP SP2/ Vista Home Premium SP1, 3.0 GHz P4, 3 GB DDR2 533 MHz RAM, 160 GB SATA II Samsung (XP), 300 GB SATA II Seagate (Vista), 250 GB SimpleTech USB (WD Drive), Nvidia Go 6800 (425/825 MHz - XP, 400/800 MHz - Vista, Vista Driver - 169.25), Dell 1901 UltraSharp FP

Inspiron E1705, Win Vista Premium, T7200 Core 2 Duo (4MB, 2.0 GHz 667MHz), 2 GB DDR2 677 MHz RAM, 120 GB Samsung HD, Nvidia Go 7900 GS - 156.69 Driver, 17” Sharp UltraSharp TrueLife Wide-Screen WUXGA