Should be ok, temporarily, but really depends on what you're doing, and how much load you expect.
The benefits of a dedicated hardware firewall is that it gives you a buffer in case of misconfiguration of the firewall, Windows, or both, temporary downtime (i.e. when/if firewall service needs to be stopped to apply an update), and vulnerabilities in Windows Firewall itself or any of the dependent services or the TCP/IP stack itself.
This isn't to say that a hardware firewall is itself immune to bugs, but a dedicated firewall is just that: a dedicated piece of a equipment that's (typically) sole purpose is to provide stateful packet inspection, (usually) routing/NAT, and other security-specific services; it doesn't have to make compromises like Windows does.