I have a Toshiba Satellite i3 Win 7 64-bit with 4 gigs of RAM. Only 5400 RPM drive though so I track to an eSATA drive. I don't do a lot of sample work on it, since it is mainly for remote tracking and simple demoing. Grabbed a PCMCIA-express TI Firewire card. I can get 24 channels simultaneous, no problem.
CPU speed and RAM wise it is fine, some ways better than my desktop Quad Core AMD Phenom 9550.
The 5400 RPM drive is a bit of a killer. I need to upgrade, but not willing to rebuild, but the 5400 works fine. But buying new, get a 7200RPM drive.
The real @#$@#er with it though to be honest is the damn screen resolution. I got the bigger 17" screen and the damn thing only does 1366x968 or some shit. That isn't even 1280x1024 that my 5 year old 17" monitors can handle. WTF!! I tell you, Cubase, Pro Tools, all suck balls at that resolution. I deal for straight tracking, basic editing. But definitely count out any MIDI or high track counts or anything based on the tiny ass resolution.
The video card can handle it, since an external I can max out 1900x1200 no problem.
The screens on most laptops these days suck! My old laptop.. I mean Pentium M 1.2Ghz 15" can do 1600x1200. It really pisses me off, and the Toshiba was't cheap, it was in the $750 sort of range. Didn't dawn on me, it said high-def uber fancy monitor and I went for it and now I get pissed off every time I use it. Yeah things are clear and movies look great, but even surfing the web for me is damn tight at that 1366x968. And I am carrying around a huge-ass 17" laptop around... grrr...
So.... when shopping look for a high resolution screen. I tell you though, I have been looking and you pretty much have to get out of the "home grade" laptops and into the professional ones, which mean extra $$$. Not a lot more but you will break the $1k mark... at least based on my shopping.