There's a bug in the API in NOISE.SYS v0.5.5. I've uploaded a fix as noise056.zip to ftp.funet.fi, so keep an eye out for it. The fix is easy. In the file "multiplex.inc" you'll see the @ReturnOk LABEL where it restores the ds, si and bp registers... at the @ReturnErr hook it only fixes the ds and si registers. Add a "pop bp" appropriately and remake the file. Sorry for the inconvenience. --Rob