Engraçado que o cmd.exe realmente contenha a resposta.
Aqui está um recorte de cmd /?
If /C or /K is specified, then the remainder of the command line after
the switch is processed as a command line, where the following logic is
used to process quote (") characters:
1. If all of the following conditions are met, then quote characters
on the command line are preserved:
- no /S switch
- exactly two quote characters
- no special characters between the two quote characters,
where special is one of: &<>()@^|
- there are one or more whitespace characters between the
two quote characters
- the string between the two quote characters is the name
of an executable file.
2. Otherwise, old behavior is to see if the first character is
a quote character and if so, strip the leading character and
remove the last quote character on the command line, preserving
any text after the last quote character.
Então, no seu caso, seria:
C:\>C:\Windows\System32\cmd.exe /C ""C:\Program Files (x86)\gs\uninstgs.exe" "C:\Program Files (x86)\gs\gs8.63\uninstal.txt""
Dito isto, também seria possível usar os nomes curtos 8.3 e, assim, truncar os Arquivos de Programas para o Progra ~ 1 ou Progra ~ 2. Ainda mais, você poderia usar caminhos relativos e primeiro navegar para c: \ Arquivos de Programas (x86) antes de executar seu comando. Seu comando então se tornaria:
C:\>cd /d "c:\Program Files (x86)" && C:\Windows\System32\cmd.exe /C ".\gs\uninstgs.exe .\gs\gs8.63\uninstal.txt"