[qbasic_forever]

IIRC Eno was really into the Yamaha DX7 FM synthesizer around the time he did the Windows 95 sound, it was almost certainly created using that hardware and then later someone mastered it to a wav file (perhaps using a pirated copy of soundforge).

[TonyTrapp]

For what it's worth, the DX7 isn't capable of producing most of the sounds heard in the Windows 95 sound. If it was used at all, it would be one out of several synthesizers.

[the-rc]

No, he used SSEYO's Koan software

[jmmcd]

He was involved in creating that, but he definitely didn't use it for this 3-second piece. It's not suitable for micro-management at all.