Windows XP will work with as little as 256MB RAM

Bought (on eBay) one refurbished D600 with 1-year warranty four months ago to gather wind speed data 24/7 for a year. Chose Dell because I've owned Dell desktops for many years and have the Windows XP install CDs that pass Microsoft update authentication without hassles. Can access device drivers and owner/service manuals easily online at the Dell website. Also, parts (used and some new) are readily available on ebay. 

Liked the first one so much, bid on and won three more in various states of needing parts. Missing parts were easy to find, and inexpensive, on eBay, so now all four laptops function with interchangeable parts for compatibility and backup, complete with new batteries, AC adapters and upgraded RAM for around $150 each. 

Windows XP will work with as little as 256MB RAM, but performance takes a huge hit since data needs to go to/from the hard drive. Upgrading to 768MB - 1GB (1024MB) RAM allows several apps to run fine simultaneously, and is cheap. Will take up to 2GB RAM (1GBx2). 

Hard drive modules and various styles of optical drive modules (CD-ROM, DVD-ROM and CDRW/DVD-ROM) are all interchangeable. 

Currently use 2nd bay large-capacity SATA modular drives for unattended daily data backups on the two 24/7 units. Have spare IDE drives (D600 internal hdd is IDE) in modules to copy internal drives for swapping if needed. 

One came with a modular bay 2nd battery that still holds a charge for extended running time. Approx 2hrs runtime on main battery. 

Two USB ports are never enough, but a USB Hub or two (or more) serve any peripherals you may have. Old-style parallel and serial ports are outdated, but my application needs a serial port, so I'm set. LCD screens are clear and bright with good contrast. Speakers are typically sub-par because it's a laptop, but speakers out jack can power a better sound system. S-video & monitor out, ethernet port. 

The D600 performs like other laptops of that era. Quite well. 

All mine came with built-in wireless, mostly 10Mbps which I just tried by connecting to HULU.com to watch a trailer. Playback was smooth, so data speed was acceptable. One laptop has a 54Mbps wireless. I'm sure downloading files, software, etc., would benefit from the faster wireless, and upgrading is easy and inexpensive. 

Because this is an older model, it's rather heavy, but it's STURDY! All mine came with various dents, dings and even a cracked cover seam, but still operate fine. With one exception: one has a somewhat common problem with D600s. Often it doesn't want to power back up for a warm re-boot (restart or resume from standby work fine.) This is likely due to a poor connection between the power button and a circuit board underneath. The workaround (pressing and holding either F7/F8, F8/F9 or F9/F10, depending on the laptop's mood at the time) allows the POST sequence to begin and it's smooth sailing from there. 

The same laptop also has issues with the 3 indicator lites (NumLock, CapsLock and ScrollLock) and the volume/mute buttons next to the power button. Pressing down in that area allows them to work, so it's likely a poor connection underneath. Volume control with system tray icon works. Someone has posted the disassembly/repair step-by-step online for the adventurous. 

I have 1.6MHz or 1.8MHz Pentium M or Centrino single core processors which perform about the same. Wouldn't want to try heavy video editing (slow) on these, but fine for general productivity software and Internet use.