Winrar Extraction Question

When I extract using my PC (i7 Quad Core processor), first few seconds, it’s okay. But when it reaches around 20% it will slow down. The time remaining will increase bit by bit for an unknown reason. But when I use my laptop (Core 2 Duo) (Old Acer Aspire5920) it extracts fine. It’s even faster than my PC. I don’t know what’s happening. This doesn’t happen before. I mean, my PC used to extract large rar files fast but now I think something wrong is happening.
Answer #1
What are the temperatures when extracting it?
Answer #2
It’s more than likely your hard drive than the cpu ?
What condition is the hdd in ? Use HD Sentinel pro v3.7