I tried running the latest 'master' branch of Fether from a Windows 7 32-bit VM using Virtual Box
In the VM I installed Git 2.20.1.windows.1, Yarn 1.13.0, and Node.js 11.7.0, and then ran yarn; yarn start
{"level":30,"time":1547981795342,"msg":"Starting Parity Fether...","pid":6128,"hostname":"IEWIN7","name":"fether","v":1}
{"level":30,"time":1547981795569,"msg":"Parity found on machine, can be run with \"C:\\Users\\IEUser\\AppData\\Roaming\\Electron/parity.exe\".","pid":6128,"hostname":"IEWIN7","name":"@parity/electron:main","v":1}
{"level":50,"time":1547981796579,"msg":"spawn UNKNOWN","pid":6128,"hostname":"IEWIN7","name":"fether","type":"Error","stack":"Error: spawn UNKNOWN\n at _errnoException (util.js:1024:11)\n at ChildProcess.spawn (internal/child_process.js:323:11)\n at Object.exports.spawn (child_process.js:514:9)\n at C:\\Users\\IEUser\\code\\fether\\node_modules\\@parity\\electron\\lib\\runParity.js:112:50\n at new Promise (<anonymous>)\n at C:\\Users\\IEUser\\code\\fether\\node_modules\\@parity\\electron\\lib\\runParity.js:109:47\n at step (C:\\Users\\IEUser\\code\\fether\\node_modules\\@parity\\electron\\lib\\runParity.js:47:23)\n at Object.next (C:\\Users\\IEUser\\code\\fether\\node_modules\\@parity\\electron\\lib\\runParity.js:28:53)\n at fulfilled (C:\\Users\\IEUser\\code\\fether\\node_modules\\@parity\\electron\\lib\\runParity.js:19:58)\n at <anonymous>","code":"UNKNOWN","errno":"UNKNOWN","syscall":"spawn","v":1}