I have a house that is covered with a fiberboard like siding, it was guaranteed for twenty five years and it is about twenty seven years old. Around the botom edge it is beginning to crumble and curl. I would like to replace the bottom two feet and am looking for the best product to use. If you have experence in this type problem I would love to hear your suggestions.

The product that you are describing is masopite siding and it WILL fall apart eventually. It is still available if you wanted to make a repair. Most real lumber yards have it - not Home Depot or Lowe's. You best bet is to replace all the siding and be done with the problem but that can get expensive real quick.

As relehew suggested, you could replace all the siding but if your looking for a quick, inexpensive fix just the bottom 2 feet could be done. I have done this and it can be difficult as it was installed starting at the bottom, then lapped up. Getting the new siding in at the point where old meets new can be a little tricky. You could use the same siding or use a fiber cement siding which will hold up much longer.