Thats not right. Could you list more of your hardware specs as the ones you listed are a bit unclear you have a i5 and a i7?
CPU: going to assume I5 2500k? Current CPU Freq ~ ghz
Video Card: 1.5 GB GDDRS NVIDIA GeForce GTX 460M
RAM: including what DDR and mhz rate, if you have 2 gbs 667 mhz ram thats your problem right there, and your cpu would be performing maybe 1-5% of what it can do.
Harddrive data transfer rate: ?
What type of lag is this, just constant lagspikes, lagspikes every now and than that freeze the screen for quite a long time, or is it a constant drain in FPS which may mean something is wrong with the video card.
With what you said your specs should be able to run the game unless your RAM is really messed up, and or harddrive.
How are loading times, does loading your homeland take like 4-8 minutes? Then it would be your harddrive data transfer rate or have some very badly damage harddrive sectors with part of the game being on one of these damaged sectors.
For testing your Harddrive I suggest using DiskSpeed32: http://software.vgrin.host56.com/diskspeed32/
Do a complete test and if you notice maga bad drops in performance in various sectors than your hardrive may possibly be at fault and inneed of repairs or replacement.
Also what is your OS? are you on XP 32 bit?