Confirm how much available disk space you have - triage a bit and run a program to clean up unnecessary files (ccleaner is my go to). Run msconfig and check for programs you don't need running at startup (itunes/quicktime/etc.) and see if you have your RAM maxed out. 4GB is good enough for most everyday users unless you're coding, run a crap load of programs or need it for photo/video editting.
Once you've done all that, run a nice antimalware scanner - I usually combo with malwarebytes and superantispyware. That will check for any mischievous infections - if you surf the web with reckless abandon or use P2P services, you're bound to get some digital crabs.
Laptops aren't meant to last much more than 5-7 years if used often. The components are built for size and to be lighter weight that their desktop siblings. As such, they're more susceptible to warping and fatigue due to extreme heat.