A lot of brand name new laptops will have some version of Vista installed on them, and most brand names will no longer allow you to customize it with Windows XP. One way around this may be to look for refurbished laptops or visit your local Best Buy or Circuit City stores to see if they still have some of the older (yet still decent) models in stock that have Windows XP as the OEM OS.
If you're willing to spend some time adjusting to a Mac and willing to spend a couple of extra hundred dollars that could be saved on a PC equivalent and go the extra mile to install software that would allow you to do the same work as your colleagues who are most likely using a PC machine, then an Apple Macbook would be a good choice. It goes for around $1,400.00.
If you want a PC laptop for the purpose of surfing the web, watching some movies, and doing office-based work with a wireless internet connection, then look for the following stuff while you do your shopping...
- AMD Turion 64 X2 or Intel Core 2 Duo processor
- At least 1 GB of DDR2 memory (2GB is recommended if you go with Vista)
- Mid-sized hard drive (around 120-150GB of storage)
- 14"-15" monitor display that can display at least 1280x1024 resolution
- Wireless internet
- Basic CD/DVD player
If you plan on keeping your laptop for a while, an optional thing to look for is one that has an accessible spot for upgrading memory (usually a panel that opens on the bottom of the laptop) as that's typically one of the first things people upgrade when the time comes for it.
There's also a difference between LCD and LED displays for the monitor. LEDs tend to be brighter, are less power-hungry but are more expensive than LCDs.
Most notebooks today come equipped with 2-4 (or more) USB ports, so you can plug a bunch of peripherals in (mouse, larger keyboard, printer, external hard drives, etc.). If that's a concern, also pay attention to the number of USB ports available.
Also verify your wireless network connection to the router. Don't want to buy a new laptop that doesn't have the right technology to connect wirelessly to your router (802.11a, 802.11b, etc.).
If you ever plan on displaying stuff on your monitor via a projector onto a screen for a work presentation or something, you may also want to verify that the new laptop has a VGA port for connecting your laptop with the projector. Optional would be a HDMI port for connecting your laptop to your HD TV or something for watching your MMA movies on a bigger screen.
Hope that helps.
