SOPC_BUILDER PATH may be incorrectly set in your environment

Hi all.

running 8.1

I get the following error :

"SOPC_BUILDER PATH may be incorrectly set in your environment"

when I attempt to build, checking past posts this seemed to relate to library locations on linux machines, I'm running on XP, the envriomental variable seems to have valid locations plus to my known has not changed in quite some time, can anyone point me in the right direction, for some reason my whole nios build process has broken on two machines!

tia,

Dave