I hope I can help here.
Processing a RAW file is, as far as I know, a software issue rather than a hardware issue. That’s not to say that hardware doesn’t play a role, for instance, the iPad Pro version of Lightroom can’t process RAW files. That might be a limitation of the iPad’s architecture I don’t know, but PCs have had software that allowed RAW conversion going back more than a decade. Is your PC really that old?
I personally use Capture One, which is an equivalent product to Lightroom, which is itself known generally as a RAW converter. There are other RAW converters around, Apple’s Aperture was one (though it’s not been disconitnued) and its current product, whatever it’s called (I think it’s Photos) will also convert RAW files for basic manipulation. DXO provides another popular package and most Nikon and Canon cameras ship with proprietary pacakges.
The differences between them all tend to be along two spectrums. The degree of sophistication in editing information within the RAW files (e.g. recovering information in shadows and highlights, changing tone curves etc) is one spectrum and then storing, organising, managing and exporting is the other.
Capture One and Lightroom are pricey because they do both really well. Proprietary software (with cameras) is free because they do both very basically. Apple’s Photos does a good job of managing your pictures but is extremely limited in terms of editing.
There are also some hybrid packages, like DxO Film Pack, that combine RAW conersion with some degree of editing but also film simulations, a bit like Instagram does with filters.
If you have a PC that is so old it won’t run any package that can offer RAW conversion, I would suggest your best option is to buy something that does. For example, you could get a Mac Mini G4 off eBay for something like £40. With your existing keyboard, mouse and monitor and the software that comes bundled with the Mac (it will likely be iPhoto which is fine as a starter package) you’ll be able to edit just fine.