Best current stand-alone firewall for XP Pro?

I had intended to use 'Online Armor Free Firewall', but recently learned it screws up VPNs, and precludes 'VirtualBox', so that is a no-go. Right now I'm considering 'Privatefirewall 7.0' ( & 'The Shield Firewall 5.0' ( Both got good reviews, but neither look to be 'standalone' firewalls, so I'm thinking they could conflict with my chosen antivirus, antispyware, antimalware, etc. If so, then my last choice would be 'Comodo Firewall Pro 3.0', which is also not a standalone, but that PCmag review says it can be made into one by disabling its 'Defense+'. Not sure what to do or which way to go, so I'm open to advice/recommendations. I need a standalone firewall that is easy for a beginner to deal with, guards both incoming & outgoing traffic, and will work with a NAT/SPI router.
Best firewall for XP?

Does Microsoft even have some obscure firewall utility freely available that I don't know about?
I have been using Outpost Firewall 2009, but have no idea how good it is, as I credit my apparent immunity from attack to the NAT/SPI-enabled hardware firewall on my MikroTik router. Outpost did let me put a stop to the incessant upgrading of BleachBit, by preventing it from calling home, so it has some use. I'd encourage anyone to deploy a hardware firewall before anything else....mine was up and running before my PC ever touched the internet.