程式編寫及軟件開發

In general, you do not need a powerful pc to be a program developer.

But, I would suggest you to get one of the duo core or duo 2 core cpu, at least 1 GB ram, >80Gb HardDisk. This would gives a better working environment, especially when you need to work in server/network environment, eg, 3 OS on the same machine. And you will need to have virtual machine to do that.

ie: say you are working with SQL server. so the 3 OS would be:
1) you original OS, which may server as a client machine.
2) you SQL server on one of the virtual machine
3) then you use another virtual machine for programming
*would suggest the 2 virtual machine have at least 384Mb, and 20Gb HDD.

You may ask why need to seperate these 3 OS, yes they may stay in the same OS environment, but working in this way would make sure your application/program will work under network condition and not just on your computer. This also applies to programming web application.

you do not need a very powerful pc for 程式編寫及軟件開發.
a normal pc will do the job.