Tintin_20131) I think both motherboards are of Micro-ATX type so i can replace the dead motherboard with the Intel . Am i right ?
Yes. However, if the 620s does not have a detachable rear IO shield, you will have to cut out an opening for the new board's IO shield.
Yes.Tintin_20132) I have a graphic card ATI Radeon 6450 with PCIe 2.0 connector. Will this graphic card connect with the new mother board ?
YesTintin_20133) Will the Intel chip i3 2120 fit into the new INTEL motherboard as the connector type is LGA 1155. And i dont know what connector type the original motherboard has ?
Yes.Tintin_20134) Is the existing power supply sufficient for the new mother board ? I am using Dual Desktop.
Tintin_20135) How do i connect the front usb and micro SD card reader in the cabinet to the new mother board ? Is it possible to do this ?
These ports connect to standard USB headers on the motherboard. Where you'll have some tinkering is with the front panel connector: you may need to substitute a set of two-wire sockets for the single large one. (You can order these sockets via mail from FrontX.)