It's pretty obvious that running this game in spots like the Clockworks is easy and doesn't require much computing power typically, but what about Lockdown? It seems to require something a bit above what OOO's has already recommended:
OS: Windows XP, Vista or 7
Processor: 1.3ghz processor
Memory: 512MB for Windows XP or 1GB for Windows Vista/7
Graphics: 64MB Video Memory. GeForce 5 series, ATI Radeon 8500. Latest video driver.
Display: 1024x600
DirectX®:
Hard Drive: 700MB
Java: Version 1.6
For starters, double the RAM and decrease the resolution to 800x600. I dunno about GPU or CPU, but I think I had better than that and struggled to get 30fps on my old PC about two years ago.