a few days ago my laptop started lagging ... alot. I opened up task manager and i saw that every few seconds my disk drive would have 100% active time with 0 average response time, read speed, and write speed and after a few seconds it went back to normal. my cpu is running at a constant 1.88 GHz (10%) and i know its not the RAM because im only using 1.2 out of 4 GB.
Please expand "Disk Activity" in "Resource Monitor" and check which application is causing maximum utilization of the Hard Disk. You might want to put a check on "Activity Time" by disabling or stopping that application.