Yes, i install vyatta on one of the desktop PC on one of the rooms in TAFE-Australia with the following specifications:

MS XP Professional SP2
Pentium 4 CPU 1.50 GHz
256 MB of RAM
Model: VECTRA VL420 DT
Prod: P5754A#810
Display Adapter: NVIDIA GeForce Z MX/MX400
Network Adapter: Intel Pro/100 VE Network Connection

brief information on vyatta thru wikipedia:

Vyatta manufactures an open source router/firewall/VPN. A free download of Vyatta has been available since March 2006. The system is a specialized Linux distribution with networking applications and management interfaces for those applications. Commercial engagements are available via a subscription-based business model which includes software updates, technical support, and training.

The Vyatta system is intended as a replacement for Cisco IOS 1800 through 7200 series Integrated Services Routers (ISR), with a strong emphasis on the cost and flexibility inherent in an open source, Linux-based system [1] running on commodity x86 hardware. Vyatta also provides a Cisco Replacement Guide on its website which shows various Cisco products and the comparable Vyatta/x86 solutions."