Do you have latest version: 0.73? Have you tried without a front-end?

Also, aren't there Windows ports of Abuse and Descent?

the Windows port of Abuse is old and unmaintained and didn't work on my Windows XP system due to the default resolution not being compatible to my LCD and there was no way to fix this...

Reasons for slow downs could be all the software you have installed and running at the same time as dosbox...

Several things pop to mind right away:

- Most obviously, something is wrong with your configs. Yes, I know you have a front end and "it's taking care of it" for you, but the first thing to do is not trust it, and just run Dosbox manually on one of the games (even with default options, should be fine)
- You're using a new version of Dosbox, or a different version than before
- Your machine is otherwise slowed down (ctrl-alt-delete, task manager, look at processes tab, see if memory and CPU are within reason)
- Your machine is throttling the CPU due to temperature or some other factor (thinks it is on battery? change your power savings options?)
- You updated a driver and SDL is getting poor response on whatever surface type you are using (try "overlay" or at least something different than what your current configs say)