You can't increase the resources, you can only limit the shrinking of it over time by limiting what apps run. Windows in general was never meant to be a high-performance OS. Its nature is that of a desktop OS. As a general purpose OS, it does this job well, despite its numerous issues.
I won't go into details on this, but if your interested you can pursue this on your own.
One way to increase the performance of Windows, is to replace the shell. Many shells are available to replace Windows' - Explorer shell, which can lower the resources consumed.
Setting up the Virtual Memory is just controlling the swap space used. This will not increase the resources but improve page swapping, by alloting a set limit on the swap space, and keep Windows from constantly resizing. This is covered on the board. Just do a search for 'Virtual Memory'
Shutting down background apps, is also covered and recently covered in a thread a few down from this one.
There are many apps which can do this for you, even then they might not be whats BEST for your situation, so it does not hurt to learn how to do these things yourself, Plus you wont be loading another app to do something which your trying to limit the apps running.
There is not a program that I am aware of that can do this on "multiple platforms," unless your referring to "multiple platforms" as meaning, different releases of Windows.
When referring to platforms, it is referring to
MS Windows, BeOS, ReactOS, OSX, AtheneOS, BSD, AROS, AmigaOS, ACORN, DOS, OS/2, Solaris, UNIX.
Programs built for a platform, such as Apple's OSX wont run on MS Windows. When such programs are built for cross platforms, they usually are ported, code was re-written, but its not the same binary.
About the only way to build a single binary and have it run on all various OS's, usually the app is built in JAVA, which then runs on the JAVA Virtual Machine, inside various OS's. Still, this is not a native binary working on 1 platform and running on another. Or, some sort of emulation is used, Such as the ability to run GNU/Linux binaries on FreeBSD. There then exists emulation in the kernel, but even then its not always successful.