A recent Official Developer Update for MechWarrior Online discusses where beta testing stands for the upcoming mech combat game, saying keys for the test are being sent out, and that tomorrow they will launch a founder's program that will guarantee entrance into the beta. Piranha Games also now offers system specifications (thanks Softpedia via Zarkonis), though they also warn the minimum may be too minimal at this time:

MechWarrior Online Minimum System Spec:

CPU: Core 2 Duo E6750 2.66GHz / Athlon II X2 245e
GPU: GeForce 8800GT / Radeon HD 5600/5700
RAM: 4 GB
OS: Windows Vista 32-bit
DirectX: DX9
HDD Space: 4 GB

MechWarrior Online Recommended System Spec:

CPU: Core i3-2500 / AMD Athlon II X4 650
GPU: GeForce GTX 285 / Radeon HD 5830
RAM: 8 GB
OS: Windows 7 SP-1 64-Bit
DirectX: DX9
HDD Space: 4 GB

Right now a duo core system is our minimum spec machine but it is also our main focus of concern. It is playable on those specifications and I have tested it myself but it is currently very much a minimum spec type of experience running on low-detail settings. It’s obvious that a Quad core system is the key as even the earliest Core 2 Quad systems run the game very well and it is our goal (since there are still so many out there), to optimize the Core 2 Duo systems to run much faster.