I don't have any .pspimage files available. But after a bit of searching on the web you might want to give XnView a try. It seems to open every file format I've ever heard of and PaintShop is mentioned on there.
http://perso.orange.fr/pierre.g/xnview/enhome.html
And it is freeware for private use.
If that doesn't work Irfanview is another popular program that has a bunch of plugins to open most any type of format and it can convert it also. It is available at:
http://www.irfanview.com
Hope it helps