1: Check the application in the Compatibility centre (microsoft)
2: Find software updates from the program manufacturer.
(if there are no windows 7 drivers, use the most recent vista driver)
3: Follow the steps in "Make older programs run in this version of windows".
4: Try running the program using Windows XP Mode. (the link in my first post, this should be a last resort). Running programs in this mode will increase the resource usage of your computer, on average when its running it will use approx 4-8% of a dual core 2ghz processor and will most likely use around 512-1024mb of ram (before running any program) on top of what vista is using.
Please list the programs that you want to run as there may be a work around that i know of.
As far as steam goes and alot of other applications, they should work. I test and trial alot of software and have only found one program that wouldnt work (out of about 100 or so). Most cases a program that doesnt work, either needs to be installed another way or just wasnt run correctly/didnt have the right drivers.