Chrome should open quickly, do you have issues with other programs lagging? How is IE? Same issue?
Since its a fresh install i'm guessing your not fragmented, try running HDTune error scan and benchmark, maybe your hard drive is slowly biting it
If its ok, updating bios and drivers could be an option. Did you get the newest drivers from your motherboard manufacturer when you reinstalled, or use the disc? or windows update?
4gb of ram shouldn't give you any major issues unless you're rendering video or something while trying to browse