1stly mayb u could some of windows feature like disk clean up and defragmenter
after that check ur hardisk health status with crystaldiskinfo
if not in gud shape need to replace new one

or mayb u can try tune up utilities...
ssd in recommended for super fast windows boot in time
never turn back after u use it..it's marvellous

How much are you willing to spend? These days, you can get a new retail 120GB/128GB SSD for around RM230,  250GB/256GB for around RM400. In day to day use there's hardly any difference between models and brands, so usually just get any you like. If your laptop has an mSATA or M.2 slot you can use that for SSD, and still keep the HDD for mass storage.

Cloning is easy really, I usually use Macrium Reflect to clone HDDs to SSDs for my clients. That program is easy to use and it's free.

http://www.lelong.com.my/sandisk-ssd-sata3...7-01-Sale-I.htm
^Sandisk X300 128GB, RM215. Decent performance, and one of the cheapest available.

Connect the new SSD to the computer using a USB cable or enclosure, run the program until finished. Open your laptop and change the HDD to SSD and the you're done.
Below is a video that shows how to use the program
https://www.youtube.com/watch?v=U0PyZIqecII
Maybe there's something else that's accessing your HDD all the time? Anyway based on my personal experience with a pretty run of the mill SSD on a Haswell based Celeron laptop, even when hammered with antivirus scans, windows update and IDM downloads the laptop is still responsive. Did this on the same laptop using the stock 5400rpm HDD it came with and it basically just gave up lol, nothing moves.

Windows Update most of the time does the trick for me.