What type of computer do you have? If it's a Macbook Pro, you're out of luck - Intel Core Duo based macs cannot run classic (i.e. Mac OS 9 and earlier), as classic was an entirely different architecture (hence "classic") then OS X, and was never made Intel-compatible (it's 6 years old anyway).
If you have a powerbook of some sort, you can install classic (though you'd have to find a copy of OS 9 on eBay) - but it puts an entirely separate and frankly dated OS on your system. Once you do that, however, Mac OS X is capable if running OS 9 in the so-called "classic environment," essentially running OS 9 within OS X itself.
What software are you trying to run? To be honest any software that hasn't been updated to OS X code is probably not worth running anyway, as it's clearly out-of-date and forgotten from a development standpoint (it would sort of be like writing software that only runs in Windows 98). And at any rate I suspect that you could find (or we could help you find) software that will do what you want in OS X.
One final note - it'll be much easier to help you if you take the time to review your posts for clarity and coherence.
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