Trend Micro makes good stuff. Could be a hardware problem. I had POS Emachines running XP years ago that started acting this way right before the 5400 RPM hard drive cratered. I would start backing up important stuff NOW while it is still working. Get a flash drive and start pulling important docs, JPEGS, music files etc.
Dump the temp files, do a disc cleanup and defrag. You can try re-installing Explorer if you think that is the problem.
By the way what brand machine is it, what OS, what processor and how much RAM do you have?
'04 Blue ZX-10R, FORKS: Race Tech Gold Valves, .85 KG/mm springs, US1 suspension fluid, Shock: Penske 8900 shock w/8760 compression adjuster, Gilles rear sets and levers, Scotts steering damper, Racefit Mega slip on, Zero Gravity screen, ZX636 Master Cylinder, Galfer Superbike braided brake lines, Vesrah SRJL17 pads, Kawasaki seat cowl, undertail kit, Oury Grips, Valentine One radar detector with Legal Speeding heads-up helmet LED.