Try reinstalling the phone's drivers, then delete everything related to them in registry or anywhere else on the computer, then make a clean install of them.
P.s. Yes, the rooting toolkit I recommended you works for many phones and manufacturers, not just e.g. the xperia z1 or our device. And sorry for the late answer. Just saw the thread here.
Phone: Sony xperia sp (c5303)
Android version: 4.1.2
Kernel version: 3.4.0-perf-g1285c6c-01149-g40c437a BuildUser@BuildHost) ) #1 SMP PREEMPT Wed Aug 14 17:10:55 2013
Baseband version: 8960A-AAAAATAZQ-40031007-13
Build number: 12.0.A.2.254