If you have a sata hdd and the bios is set to ide mode rather than AHCI then this will reduce performance quite a bit. Unfortunately, you cannot change to AHCI mode after installation, you would need to do a clean install if you change the setting.
Sometimes, though, the setting is a dual mode for both IDE/AHCI then it might be set to IDE, try to change to dual mode. If it doesn't work, you get a BSOD then just change back to IDE mode.
You don't get good performance if the PSU is 264 watts.
Wattage does not tell the whole story these days.
There are 350W PSUs that are superior to some 500W variants. Manufacturer, weight, Amp distribution, noise & heat levels, ATX specification, form factor, modular connectors etc .... are all things that need not be overlooked when comtemplating a PSU purchase. Hardware, especially graphics cards must be considered.
Try defragmentating your HDD, run CCleaner, check in the Task Manager in the Processestab if there aren't any weird programs running.
Try hitting the CPU Usage a few times so it sorts out the highest usages on the top