A lot of things could contribute to it taking longer.
Age of computer and more specifically the hard drive
Dust and dirt build up on the CPU / and heat sink can cause the CPU to throttle down
If it's a spinning disk hard drive the fuller the drive is can cause additional seek latency to find and remove data
Potential malware running on the system
Corruption in the operating system
If this computer hasn't had a fresh install of Windows in a long time, I'd suggest backing up data and re-install Windows. That should eliminate several of the potential reasons for the slow down.