I have a parallel port adapter connected to my PCMCIA (Cardbus) socket, and I have a device plugged in there which can light up in different colors, controlled by values sent to its I/O port (0xFEE8). Now, the reason I posted this in the software section as opposed to the hardware section is I'm looking for a program which can make the light blink when I get a new email. If anyone knows of software which can make it work as a general-purpose status indicator, such as indicating when the computer is locked, when the battery is low, etc. Please post if you know of anything like this!

You're most likely gonna have to get your hands dirty.

I'm looking for a program which can make the light blink when I get a new email

Never seen one. However, the checking email part is simple. There's examples on MSDN (e.g. here in an old Coding4Fun article), various community sites like codeproject.com and so on.

controlled by values sent to its I/O port (0xFEE8)

That is even simpler, but you'll have to use something like PortIO to do it.

If anyone knows of software which can make it work as a general-purpose status indicator, such as indicating when the computer is locked, when the battery is low, etc.

Most of these sort of things are also easy to get using technologies like WMI (as for the computer being locked you could probably manage something using the task scheduler)