Just a thought but try going into your Performance preferences (Edit>Preferences>Performance) and make sure most of the available ram is set to be used by Photoshop. 8gb isn't very much if you have other programs open at the same time, and/or are working on large image files.
Hi Steve, thanks for taking the time to answer me. Unfortunately, I already set available ram for Photoshop to 80%. With no success..
How large are the files you are opening?
Your OS is using a chunk of your 8gb ram, and then you are using 80% of what's left. Probably that's not a lot. Photoshop will start using the hard disk for scratch disk when it runs out of ram. You'll want lots of empty hard disk space for Photoshop to use for scratch disk. If your hard disk is nearly full that could cause some problems too. Other than adding more ram and making sure you have lots of empty hard disk space, I'm not sure what else to suggest.
Thanks again for your time. Files are 25 mb each. But I look into that harddrive idea. Not sure what else to do but adding ram. Still strange as collegues with a laptop and 8gb seem to have no issues with speed. Thanks anyway!