I have WiFi router set up. Both my phone and Windows PC connects to the same WiFi. So I tried ES File Explorer to copy shared folders from my Windows PC to my mobile. However transfer speed goes as high as 570 KB/s but not more than that. Since I configured my WiFi router to allow speed as high as 300 Mbps I am guessing why it cant hit the Mbps speeds. What can I do improve on my speed since I move movies worth in GBs and it takes almost an hour or more. Is it limited by the speed of the mobile and its internals?
Your phone seems to be a bit older as it runs Android 2.3 - therefore I assume it does not support any faster WLAN connection than 54MBit.
Hence the theoretical maximum would be 54MBit = 6.75 MByte/sec but only if you have just a router and a phone. With your PC in the network each device gets less than that.
Depending on the network protocol used you also lose a lot of speed. SMB/CIFS as used by Windows shares is very ineffective. Better use FTP protocol and suitable client for the best speed.
If that does not improve the performance I would suggest using an sd-card in and sd-card reader directly attached via USB 2.0 to your PC.