This review is written from the perspective of a laptop technician. If you want to know what an industry professional thinks of this laptop then read on.
PRO's: The Dell C640 was the model that made Dell famous. It's fast, user friendly, and simple to work on. It's not like some other manufacturer's that have a ton of bugs in their software. The drivers that run all the hardware are simple and trouble free. It's one of the most stable laptops I've personally seen. If you've ever owned an HP or Compaq there is patches for the patches to fix the bug that still exists. It's nice to just have things simple and problem free. As far as upgrades, they are endless. You can go up to a 2.4GHz Pentium 4 processor, I've seen it done, but they don't come stock like that. The only downside to the processor upgrade is it creates more heat and uses more battery. You may want to use some quality thermal paste on the processor during the upgrade. You can add up to 1GB of RAM. You can put a wireless card in the mini PCI slot located in the bottom panel of the laptop. You can add a second hard drive or second battery in the CD drive slot. Plus you can find DVDRW drives available for this model on eBay. The DVD burners were not made by Dell, keep that in mind. They are built by other companies and sold on eBay. Basically you can do just about anything needed to this machine to make it fast.
Con's: There is a common flaw in this model. The design of the laptop didn't adequately cool the laptop. Sometimes you will get random shut downs and the laptop won't start back up right away until it cools off. We get around this issue by using a program called Speedfan. It's a free download that monitors heat on both the hard drive and processor and can alter the fan speed and frequency to provide extra cooling. Once you install the program on the main screen there is a check box to automatically control the fans, just check that and your set. It's not a bad idea to put some thermal paste on the processor to prolong the life of the laptop, if that's something you feel comfortable doing. The processor is under the keyboard. Remove the 6 screws on the bottom of the laptop that are labeled K and that will get you to the heat sink. Remove the four screws to the heat sink and carefully lift the heatsink up. There is the processor. Don't try this if your laptop is under our warranty, lol.
Final Comments: The C640 is a very user friendly laptop design that' s had years of proven reliability. It has the heat issue, but once resolved it's one of the most reliable laptops Dell ever made. It's perfect for the novice computer person that likes to tinker with computers. All the parts are easy to get to. The screws are clearly marked. There are only 3 different size screws in the entire laptop, so that makes it easy to work on. Parts are cheap and easy to find. You can upgrade to internal wireless. A lot of them didn't come factory equipped with the card, but the slot is available on the bottom of the laptop. We have the cards in our store if you are interested. Just let us know you have a C640 in the checkout instructions and we'll choose the right card for you. The choices we offer are just wireless G or wireless B. All in all this laptop can tackle any task and it's one of the best products Dell ever made.