Happened to a neighbor lady that I just spoke to yesterday. She had some older OEM PC, maybe a Dell, maybe an HP or something, it was so long ago that I don't remember. We had a thunder+lightenining storm, and after that, her PC wouldn't turn on. I replace the PSU with a good ole' Rosewill 400W ATX PSU (thankfully, PSU on that PC was a standard type), and it was working again. (*She paid me for the PSU and fixing it.)
So, yeah, odds are fairly good that the PSU took the brunt of the damage. However, be aware that, as with all things lightning-related and electronic, there may be more and unforeseen damage that shows up later on. That said, if you replace the PSU, and it POSTs and boots Windows again, you're probably good to go.