HP Notebook Memory/Hard Drive Question

Hello all. I have searched all over and cannot find a conclusive answer on this. I have an HP dv9580us laptop I purchased in September of 2007. All the documentation I've found swears up and down that 2gb is the maximum memory this laptop can have and yet at the time I bought it 4gb versions were available (I tried to order one through HP which didn't work out at all) in the same 9000 series. I had my heart set on 4gigs but had to buy a PC immediately and had to settle for this one. It runs Vista Ultimate 64 bit and anyone running Vista Ultimate knows it likes 4gigs much better than 2. I have heard there was a bios revision back in 07 that made it so it would recognize 4gigs which I think as F.27 but when I check HP's site for this model it doesn't show that version. I have heard that 9000t and z series can take advantage of said bios update but mine is apparently a u series and seems it cannot. Does anyone know for sure? Aren't all 9000 series roughly the same or are the motherboards different somehow? It would seem ridiculous to me for 32 bit 9000's to be able to take 4 gigs and the 64 bit 9000 not be able to. Also can 7200 rpm drives be used in these laptops? I have heard that power and heat would both be serious issues and both of them already are on these laptops. My battery life at its peak was 40 minutes and I only use it at work where it is plugged in full time so power im not so worried about but heat could be an issue. Please advise and thanks in advance!

~Jeff~