Nitro for Windows is not a single, widely-known program. There are several possibilities depending on the context :

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It could be a typo or a misremembered name:

Perhaps you[SQ]re thinking of a different application related to Windows performance, gaming, or productivity. Could you provide more details? For example, what does it do? Where did you hear about it?

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It could be a specific program from a smaller company or individual developer:

Many smaller programs exist that don[SQ]t have widespread recognition. Without more information, it[SQ]s impossible to identify this.

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It could be referring to a feature within a larger program:

Some software packages might have a component or feature called "Nitro." Again, more context is necessary.

To help me understand what you[SQ]re looking for, please provide additional information.