Example E1505 configuration from Dell Home:
Start with the base system, no bundle savings.
T7200 2.0Ghz Core 2 Duo Processor
Windows XP Media Center Ed.
Free Upgrade to Vista Home Premium
15.4" UltraSharp Wide Screen SXGA+ with true life
1GB Memory at 533Mhz
100GB 7200 RPM Sata internal hard drive
8x CD/DVD Burner
256MB ATI Mobility x1400 graphics
85 Whr Primary Battery
Intel PRO/Wireless 3945a/g
Dell Wireless 355 Bluetooth Internal
Base 1 Yr mail-in warranty
Base price: $1536
20% off coupon price: $1228
This configuration does not include upgraded memory (it turns out it's cheaper to buy elsewhere and the base is 1G), upgraded software packages (also cheaper to buy elsewhere) A/V packages (use AVG Free), or any uplifted warranty.
For memory, when you're ready for an upgrade we'll find you a 2x1G 667Mhz memory upgrade currently going for around $200. Dells 2G upgrade is almost that much and is slower memory. Swapping out the old memory and replacing it is trivial. (One screw on the bottom of the laptop. Plus the DIMMs are keyed, so you can't put them in the wrong way.) When you decide to upgrade the memory, you can sell the old memory on ebay if you are so inclined.
For software packages, if you want Office, and you have a student or teacher in the house, you can buy MS Office Student and Teacher edition which is relatively cheap and includes PowerPoint. If you don't have a student or teacher or can't live with the restricted terms on the student and teacher edition (MS's terms disallow it being used for commercial purposes), you can buy an OEM version of Office, cheaper than what Dell sells it for. (Same with Works Suite.) Or you can decide to try Open Office, which is free for individuals and is compatible with MS Office. Your software choice has nothing to do with the cost of Vista or being vista ready.
The warranty is up to you, and the price has nothing to do with Vista.
This is a very nice configuration at the price and will no have no problems running XP or Vista, though for Vista, you will probably want to upgrade the memory, but you can do that later.
-David