What is your graphics card?
There are a number of factors that will and an affect on graphics. The GPU is typically the biggest factor.
If your trying to draw the raster through a network that may also be part of it. Try putting it on your C: drive and try it.
However, there are a number of basic computer practices that have an affect.
You should also defragment your HDD and Run Disk Clean up on a regular basis.
Also clear the history and cookies of your web browsers.
Occasionally run Error Checking on your HDD
Restart your machine
Having a lot of add on's running for a browser like IE also decrease performance. Go into Advanced Settings for IE and reset IE. This will remove add on's. But you may want to consult with your IT department first.