"404 Error. Please try again." upon compile

How long is your user name?
I guess this is the only thing that should make the default path for that installation exceede the limit.

Have you tried the CLI installer?

Particle is still looking for willing guinea pigs that will test this and throw ever new issues back at them :wink:
Windows 7 is a bit of a bitch tho' - I've got it on 8.1Pro64 and 10Pro64 without issues.