No one else seems to have answered, so I'll have a go since I also use a Sony PCG V505DX lappy (dual boot).
First of all, wireless LAN's. Linux is not compatible with *all* wireless cards, especially Sony's inbuilt laptop card. I don't know if your Netgear card is compatible or not, but from experience I don't like Netgear too much and have kept away from it.
If you need to use wireless (and you should, since it's a laptop
), I like the Orinoco Gold A/G/B cards, or even a Linksys G with antenna adapter. The Orinoco Gold isn't cheap though, so it depends on the money you want to spend.
Which distro to install? Well, that would depend on if you've used Linux before or not. Personally, I like SuSE, Slackware, and Debian for a starters, but if you go more advanced, there's always Gentoo :P
I use this laptop mostly for buisness, I am a remote network engineer, utilizing all windows clients.
I think you'll find that all the needs you wrote down are taken care of in Linux. If the distro doesn't come with it on install, you can always download the packages later.
Connecting to Windows networks? Without any additional setup I can do this with my home network (using Windows 2000/ XP Pro) from my laptop using Linux SuSE. But I wouldn't take my experience as word for future possibilities. Obviously, if you can connect to the network you'll be able to send files over the network, so that problem is answered.
Browsing Internet? No problem with Linux distro's: Mozilla browsers, Konquerer, Netscape (why anyone would use the old NN, I don't know), Opera... pretty much anything but IE, but is that really a loss?
I would like to also have, but not necessary:
Play music? Distro's come with Multimedia all the time, including Kaffeine, an audio player.
Chatting? Depends what client, but all Windoze clients, such as MSN, AIM, ICQ, IRC, etc, are all covered.
I am thinking of settig this machine up as a dual boot machine with WinXP or 2000, haven't decided.
Which should I install first?
Windows, always. Then your Linux distro.