Oooooh Windows 95 had the best startup sound of all Windows, by freakin' far. 'Tis was a true work of art. I've had 10 years of formal musical training and I can tell you that it's really epic sweet. Ok? It's good. There.
Too bad it was compressed in 8-bit wav (like pretty much all sound at that time, mp3 was too heavy to be decoded in real-time, so everything was raw PCM, but mono 8-bit. It was terrible.).
Some insight into its composition (from Raymond Chen's blog):
The sound was very relaxing and therapeutic.
I've added it.
1654-Windows_95_Startup-Microsoft-2077254053.zip 96.07KB 95 downloads
Forgot to add, however here is a small file (no installation required) than can change your start-up sound without going through hacks,