I have a lenovo g400 laptop and i want some upgrades. I have intel i3 processor .my question is, can i update this to intel i5 or i7 ? .i have 2gb ram and i want to upgrade to 4gb+2gb? .is this okay ? :)

A lot depends upon whether this has the HM76 or HM86 chipset. The HM86 can support i3, i5, and i7 chips, but the socket may be a problem. As for memory, it should be able to support 4-16GB of RAM, depending upon the simms that you install. Go into the BIOS and list out the hardware/chipset specs here and we can probably tell you better how much you can enhance this system.

This is what i got in my bios:

Product Name: Lenovo G400
Bios Version: 78CN19WW(V1.07)
EC Version: 78EC19WW(V1.07)
Lenovo SN: Cb25043813
Board Number: 3203769204706
CPU: Intel(R) Core(TM) i3-3110M CPU @ 2.40GHz
System Memory: 2048 MB
Hard Disk: WDC WD5000LPVT-24G33T1
CD/DVD Rom: MATSHITA DVD-RAM UJ8D1