One of the things I need to do a lot with building and repairing computers is to remove a hard drive and attach it to a second system to do an offline virus scan or attempt to recover data. For SATA drives that is easy, I have a couple of eSATA docks which allow me to slide in any SATA drive without a problem. As SATA hotswapping is not a problem (at least with AHCI mode in the BIOS), this allow me to boot the known working system and get the virus scanner an everything up and running before attaching the drive. Hopefully this should detect any bootblock issues etc.
I still have need to test IDE drives, and they are more of an issue as I either have to dismantle the second PC and connect it internally, which means it is present during boot which isn't ideal, or I have to mess around with USB-IDE adapters and external power supplies which isn't ideal either as it is a bit of a faff and is limited by USB speeds. I got a couple of removable IDE caddies which improved things as it made it easier to connect to the PC, but still meant I needed to have the drive present during booting.
For Data Recovery or Virus problems, see