Kat Delong replied to my initial query on upgrade options for the Sony Vaio VGN-SZ3XWP/C. I have two follow up questions. First, she mentioned a hard disk upgrade of a 7200rpm drive but did not mention a max hard drive size. Also, will copying/ghosting the existing partitions in my hard drive then copying them over to the new drive work, i.e. after the ghosting process I stick in the hard drive and just boot as normal? Second query is, I want to upgrade the internal wireless card. Will this laptop model accept the Intel® Wireless WiFi Link 4965AGN, and is it a simple swap over? Are there any drivers to download? Is it worth upgrading the internal card as opposed to just getting a USB or express card supporting the 802.11n standard?
I hope my original advice helped you some. Let's see if we can answer these questions. Because the model you have is for the UK market, I had to base most of my answers on the US versions of that laptop, but most answers will apply for the Sony Vaio VGN SZ line as a whole.
Hard Drive Upgrades
The example I gave you on the hard drive was based on replacing the existing one with a Seagate 100GB hard drive with 7200 RPM. After looking at all of the compatible hard drives, it looks like you can go up to 500GB SATA/300 7200 RPM if you don't mind spending the extra money, or go for a 250 GB SATA/150 7200if you want to go for something in between. Like most things, this decision comes down to need and how much money you want to spend.
Ghosting Hard Drives
As for copying your hard drive to the new hard drive, there are a few ways to go about it. Most people use a program like Norton Ghost or Acronis True Images. It is easier to ghost on a PC because they have extra IDE ports to copy to. On a laptop, you will connect the old hard drive to the PC then use the ghost software to copy the old hard drive information to the new one and then install the new one in your laptop. If you already own the ghosting software, this is probably the way to go. If you need some help, Radified.com has forums that deal with the use of all versions of Norton Ghost. You will also need two laptop hard drive to EIDE adaptors.
If you haven't bought ghosting software yet, you may want to look into getting a data transfer kit that is easy to use and is specifically for your situation. You transfer the data from the old drive to the new one using an external enclosure and a USB cable connected to the laptop's port. You then run the cloning software that is included to copy the info from one hard drive to another. You can then use the enclosure and the old hard drive as an external backup for your laptop. There is a popular one called EZ-up that is available from Drive Solutions for about $45/US.
Wireless Card Upgrades
Changing the wireless card is really up to you. I often subscribe to the "if it ain't broke" theory on these things, but if you are having trouble with the one that came with the Vaio, then by all means change it. From what I can tell, the Intel you name should work with your laptop - many Vaio models are shipping with that particular card installed, and it should work with the Intel Centrino Duo technology. Apparently Intel is keeping the support and drivers for XP, even though for awhile it looked like they were going strictly with Vista.
Hope that helped and you get the laptop you want after all of these upgrades.