I am unable to link my phone with my laptop. When I connect the USB it says st25i camera connected. I use a Sony Xperia U model and my laptop has Windows XP OS. What can be the issue?
Most probably driver issue, following resources may help you
Right click on My Computer icon (on desktop) then Click "Manage"
Click on Device Manager, and select "Portable Devices" from the list. Double click on Device Manager and select ST25i (Your phone Device) from the list.
Right click on ST25i (Your phone Device) and click "Update Driver..." from the list (which will open a Hardware Update Wizard)
Click "Install the software automatically (Recommended)", then Next and the wizard will search for correct Update automatically.
Click on Finish.