There is a small chance that when you installed this system the ram did not set itself to the correct speed, it couldn't hurt to check in the BIOS that it is set correctly. It is a small, but noticeable difference if you ram is set to 1333 and it is supposed to be 1600. The timings are also important, 9-9-9-27, or what ever it is supposed to be. Check with ram manufacturer to get correct timings.
Another thing is the hard drive. Did your old system have a 7200 RPM drive and this one is 5400 RPM? That could make things feel slower too.
Hi. My current computer has i3 3220, 4GB Ram DDR3 1333Mhz cl9, HDD 1TB 7200rpm, Nvidia gtx 560ti (reference, no OC), PSU Thermaltake TR2 600w. My old computer had phenom ii X6 1045T, 8GB Ram DDR3 1333mhz cl9, HDD 1.5TB 7200rpm, hd 6870 (non reference with OC), Thermaltake TR2 600W.
Sometimes when I'm surfing the web, when I open a lot of tabs the computer start to "pause" and that's annoying, and sometimes I'm writing and what I wrote starts appearing on the screen like 2 seconds after I wrote that... my old computer never did that... I regret a bit having listened to the advice given to me in some forum about buying the i3, mostly because the 1045T costs now 89USD on Ebay (the shipping to Colombia would have cost around 20USD) , and the i3 cost me around 140 USD here in Colombia... it was actually more expensive... I thought that the intel solution would be a lot faster...