I have a moister problem under the house. I think that I have located the place where the water in entering and am having it repaired. I also have a problem with moisture around where the registers come from underneeth the crawl space and up to the floor. Some of the subfloor looks to be rotten. How can I fix this? Do I have to pull up the wood floors, or can it be fixed from underneeth? Any help would be appreciated.

Yes to replace the subfloor, the finished wood must be removed.

can you just pull up the specific planks or does the entire floor have to be removed?

Just where you need to fix it.

Thanks!

IMO, subfloor repairs, which are structural, should be left to experienced carpenters or contractors.