PSD is a Photoshop file type. If you have Photoshop, open it in that and convert to jpeg. If you don't have Photoshop and it won't open in any photo software that you may have, I'm pretty sure that (recommended) freeware program Irfanview will do the trick.
Good recommendation LeMarchand, Irfanview will do that and heaps more, especially with the free plugins added.
In addition.... when you do a screencapture (PrtScr), Irfanview will also have that in memory so you can do a simple 'paste' from the Edit tab, a lot quicker then starting up the Paint prog.