ADFBlitzer is an Amiga program you need to run on the Amiga. It won't work on the PC.

The Goliath PSU is a very good one to get. I have this for my A1200 and it works well. It is a 200W PC PSU converted to work with the Amiga and will supply more than enough power.

If your A1200 came with an A600 PSU then it is even worse. The A600 PSU is even more under powered than the A1200 one, and only supplies about 18W. You can easily tell if it is an A600 PSU because they are bigger then the A1200 ones and very light to pick up. IN contrast the older A500 PSUs were very heavy.