Well, I went out this weekend and bought enough 3/4" red oak to do my entire first floor. I was thinking I pull the carpet up, throw down some felt paper and get going. Once I removed the carpet, I noticed particle board over plywood! I did a search and it seems as though the best thing to do is remove it and put a suitable underlayment in it's place (which I was afraid of). I'm not sure if the plywood is 3/8" or 1/2" but the floor joists are 16" on center. The particle measures right around 1/2" thick. My questions are:
1. will the plywood support the weight of normal traffic while I'm tearing it out before I get the new underlayment on top?
2. is it alright to go with osb since it's quite a bit cheaper than plywood?
3. will I need to place rosin paper in between the two?
4. what's the best way to get the ring shanked nails out between the floor joists. I'm concerned that when prying again the thin subfloor with my pry bar that I'm going to break through the underside.

thanks for any help you can provide.

1: No problem about the plywood supporting you and your equipment while you are prepping this job.
2:Ya you can, Im not a fan of OSB but it is acceptable as an underlay for hardwood.
3: No, it would go on top of the final subfloor assembly.
4: Unlikely. Use a wonder bar or similar.

I like to cut the particle board into grids and tear it out that way. Seems to be easire for me.

Thanks a ton! So if I'm not putting rosin paper between the original subfloor and the new underlayment, Do I have to glue it to keep it from squeeking or just screw it every 6-8 inches throughout the entire room? Thanks again for your help.

I had thought about that. Right now, I starter tearing it out where there was tile on top so I can see the nail heads due to the thinset. Once I get under the carpet, they should al be visible and I will definately try and see how it works. Thanks so much for the help.

Screws, at the spacing you are thinking about, should be sufficient.
Glue is an additional cost you may wish to avoid, but certainly wouldnt be a waste. Use a urethane glue in tubes in a zig-zag pattern.

Great thanks. I just called Lumber Liquidators today and even though my order has already shipped to their store, they said that they would still let me change to an engineered floor if I wanted. These people are absolutely wonderful to work with and I believe are truly in it for the customer's best interest, not just their own. My friend had the exact same situation with his floor when he pulled up the carpet and he went with an engineered floor that looks and feels (to me at least) just like solid hardwood but he was able to go directly over his particle board floor. I'm really considering this and my question is can I just use standard 15 lb. felt roofing paper still as an underlayment? The guy at the store said they sell a felt paper that's a dollar a foot but I couldn't tell the difference between that and roofing paper. Also might be worth mentioning that I have a basement, not a crawl space.

Well, I've decided to man up and go with the original plan of solid hardwood. I started tearing out the particle board in the entry way and closet last night and it wasn't too bad. I have a friend coming Saturday and we are going to get all the carpet out so we can tear out the particle board and add the new osb. I have 1/2" plywood subfloor that I will be leaving and then adding 1.2" osb (the same thickness of the particle board I removed) so hopefully with all this done and 3/4" hardwood on top, the floor should be solid, sturdy and better than new. Thanks for the help, guys. By the way, I've read nearly every website I could find but do you have any secrets of the trade I should know before laying the new hardwood that would save me time or headaches??

There are no "secrets" to installing a hardwood floor but there are lots of tricks. These are related to specific things you may encounter. So if you encounter or anticipate a problem, just hold up the install a bit while you check with one of these clever guys on this site.

I have been doing a lot of reasearch and the only thing I'm not 100% sure about so far is how to start the first couple of rows until you can fit a stapler in. I have a brad gun that I could use to face nail but do you have to hand nail through the tongue for the first couple rows?

Ya, but you can use the brad nailer you have. First board you face nail near the groove edge so that hopefully your wall trim will hide these small holes, then suppliment the face nails by nailing along the tongue edge with your brad nailer at 45 degree angle. The second board, nail along the tongue edge again. The third board you should be able to use your nailer.

That's what I was hoping to hear. So will 18 gauge brad nails work alright for that?

Well 16 gauge would make me feel a lot better. I generally only use 18 gauge for fastening trim such as 1/4 round. Use some PL type adhesive to increase the secure-ness of the first and last boards, if you are going to use the 18's. A urethane type adhesive will maintain some flexibility of the floor system.

Well, it's been a while but my entire first floor minus the kitchen and bathroom are finally done. To date, I have done the entryway and closet, living room, l-shaped hallway, bedroom and closet and office and two closets. I was not the easiest thing to do especially with a little one running around but I finished it up this weekend and hope to post a couple pics once I figure out how. The main issue I had was the particle board underlayment but I removed it all and laid down another layer of 1/2" plywood and it was well worth the extra money of particle board. With two heaping truckloads of flooring, nearly 8000 staples, a lot of money in other tools, screws and finish nails and a lot of cussing and muscle cream, I'm officially finished with hardwood in this house. Thanks to everyone for the great advice. I don't think I would have been able to do such a quality job without it.