Successfully concluded the simultaneous disk-replacement surgery on both of my personally-owned computers.
There was the Lenovo laptop, which came with a 500 GB Western Digital, sliced and diced into a few partitions the way they usually ship these days, but with most of the space in one main partition, which had Windows 7 pre-installed. This one crashed. Badly. Couldn't even boot. I did manage to get all the useful data from it, by booting from a Linux CD, mounting the hard drive, and copying the data to a USB. But the OS seemed hopelessly f***ed, and wiping the disk followed by installation of either Windows XP or Vista failed. Went to the shop, got a 500 GB Seatgate drive, and installed it. Apart from the anxious moments when the computer wouldn't boot at all (probably because the battery was too depleted), works fine. Slowly building this one up to where it should be.
Since I had to go to the computer shop anyway, I decided to get a supplemental disk for the desktop. It came with a 250 GB and Windows Vista; I promptly wiped it, partitioned the disk, installed Windows XP and Linux on it. The Windows C drive was a bit over 20 GB, which seemed like plenty at the time, but it's bursting at the seams now. A while back, I turned on compression on the C drive to try to stave off the inevitable for a little while longer. So I got a 2TB internal disk, and installed it (in addition to, not instead of) the 250GB. Disk comes with no screws (got some from some old computer parts) and no power cable (no spare! stole the power cable going to the CD/DVD drive, which stubbornly refuses to work without power). Works fine, came up the first time. Split it into four data partitions (three NTFS and one EXT3), so that the 250GB drive could be used entirely for OS partitions. Expanded the 25GB c drive to about 100 GB, expanded the existing Linux partition to 70 GB, and created a new Linux partition of about 70 GB. Partly done with the aid of gparted software.
It is taking a day to uncompress the drive :(