For stories, Microsoft Word
For scripts, Final Draft 12
As a substitute if Microsoft word isn't work, LibreOffice or Google Docs

MS Word is only included in some OEM bundles, a basic windows computer doesn't usually come with the office suite. You can try the web version of word if you have an outlook account, otherwise try WordPad or as Zenion suggested, look at LibreOffice, OpenOffice or Google Docs (careful with Google Docs though their copy right and anti-wrongthink/anti-cp/anti-history content AI has recently been going nuts and blocking/deleting a bunch of stuff it shouldn't lol)

Personally I've been writing in Notepad++ but it's not exactly the best environment to further freeform creativity as it's meant for code.

There's also a free alternative to MS Word called Kingsoft. Beyond price and the lack thereof, I literally can't tell the difference.

I am extremely old fashioned: I write my furry stuffs on Notepad.

For other work, Google Docs is pretty good and it's in the cloud, which helps a lot.

Open office is good.
Nothing special, but it does it's job.