Welcome to the forums
@poroseki .
If you've got the laptop model and specs that would be helpful. Which OS are you using?
Modern laptops will intentionally throttle their speed to either save power, or prevent overheating. I imaging it's unlikely you've limited the speed in the BIOS (but you could check). Likewise, it would be unusual for Windows to throttle the speed and lock it there, if more power is required.
How are you confirming the CPU performance? If it's Windows 10, can you take a look Task Manger (right click taskbar to access it) and then take a look at the Performance tab > CPU when you're under load. As the % utilisation increases, your CPU Speed figures should adjust upwards as required. If this doesn't happen and you're stuck at 0.75Ghz when under 100% CPU load, then there is a problem.
Could your laptop be overheating? That would cause these problems. If you download and install CoreTemp (
http://www.alcpu.com/CoreTemp/ - it's free), can you please let us know what the temps look like (a screenshot perhaps). If it's getting too hot, the CPU max speed will be limited to prevent damage. Taking a vacuum cleaner and gently cleaning the laptop exhaust ports may clean out some of the dust blocking airflow and improve things.