First, the maximum size of an internal hard drive for the D420 is limited only by the current state of technology in 1..8" drives. That said, let's move over to the real world.

You should be able to install any 1.8 inch hard drive as a direct replacement for your current 60 GB drive, which is probably a Toshiba MK6008GAH, as long as the replacement supports the PATA interface, has a ZIF connector, and has about the same outside dimensions as the current drive. A web search on "1.8 PATA ZIF" will yield numerous results. For example, a number of sellers offer the 120 GB Toshiba MK1214GAH at prices ranging from US$125-188.

I took an entirely different approach. I stuck with the original 60 GB internal drive and bought a Seagate FreeAgent Pro 750 GB external USB drive (available for about $100). When the internal drive gets too full, I just move a bunch of useless stuff over to the external drive. I don't ever look at much of what I put on the external drive, but I likely wouldn't have used it when it was on the internal either. These things are reliable out of the box and now come in even larger sizes.

Good luck,

Ted

It uses a 1.8" hard drive -- NOT the more common 2.5" format - so your upgrade choices will be severely limited. 

Toshiba is about the only maker left and as I recall, the drive is PATA, not SATA - and needs a specific type of connector.

http://sdd.toshiba.com/main.aspx?Path=StorageSolutions/1.8-inchHardDiskDrives

Did you find a suitable replacement for your D420?  Will any Toshiba 1.8 HD work?

Be careful - there are SATA and EIDE (only the latter will work) and even with EIDE, there are a couple of types of connector -- the one used by MP3 players isn't the same as the one used in the notebook.

First, the maximum size of an internal hard drive for the D420 is limited only by the current state of technology in 1..8" drives. That said, let's move over to the real world. You should be able to install any 1.8 inch hard drive as a direct replacement for your current 60 GB drive, which is probably a Toshiba MK6008GAH, as long as the replacement supports the PATA interface, has a ZIF connector, and has about the same outside dimensions as the current drive. A web search on "1.8 PATA ZIF" will yield numerous results. For example, a number of sellers offer the 120 GB Toshiba MK1214GAH at prices ranging from US$125-188. I took an entirely different approach. I stuck with the original 60 GB internal drive and bought a Seagate FreeAgent Pro 750 GB external USB drive (available for about $100). When the internal drive gets too full, I just move a bunch of useless stuff over to the external drive. I don't ever look at much of what I put on the external drive, but I likely wouldn't have used it when it was on the internal either. These things are reliable out of the box and now come in even larger sizes. Good luck, Ted

This is very helpful - thanks!  I agree that using an extenal is the best way to go with the limited drive in D420.  That said, I would like to replace the current drive and start fresh for a Windows 7 install.  The advantage of a larger drive like the MK1011GAH (the 100gb) is the size of the buffer going up to 8mb.  I'm hoping this speeds up the drive's response a bit.  It looks like the largest with support for PATA ZIF is the drive you mention.  I have found the 100gb significantly cheaper than the 120gb.

Steve

Dear Steve.. did you replace your HDD with 100GB and did it work fine? DELL support says it can support max 80GB + they are out of stock!!

I replaced the stock 80gb drive with the Toshiba MK1214GAH which is 120gb.  It works great because it's has a ZIF connector. I installed it in about 10 minutes (you need to be very careful with the ZIF connector), loaded Windows 7 and the machine is running great. I found the drive on sale at Superbiiz for $100.  Regular price is $115.  No tax and free shipping made it a great deal.  The cheapest I could find the 100gb was about $85-90 shipped, for an extra $10 bucks I went for the bigger drive. I don't know why Dell would say it only supports 80gb. 

Steve

Thanks Steve. Hopefully I would find the drive in India.

My D420 came stock with a 60GB drive.

I tried a Toshiba MK1231GAL 120GB drive in it and the windows install disk said there was no drive found.  I ghosted my old drive on to the new one but got a BSOD when the machine tried to boot (saw the Windows splash screen before BSOD).

What version of BIOS and specs is your D420?

Mine is a CoreSolo running A06 which seems to be the latest BIOS for my service tag.

Same spec as yours wit A06.  I found that it was necessary to make sure the ZIF connector is properly locked into the drive.  Since you got a BSOD the second time, perhaps the first time it wasn't properly seated?  I'd try booting off of the Windows 7 DVD again and see if it recognizes the drive.