It never hurts to have more then one or two drives/burners I myself have 8 on hand, you will find that some drives read better then others and some burn better then the rest
As far as the computer slow down it can be related to a few things.
1...The drive may be in PIO mode for the Transfer rate, so check that first...you should have it set to DMA mode
2...system wide maintenance is needed
Do a Disk cleanup using the Disk Cleanup utility found at -> Accessories/System Tools on the Start/All Programs
after running that utility run a registry cleaner..(CCleaner) is free and very good then after you run the reg cleaner you will want to run the Disk Defragmentor utility also found at the same location as the Disk cleanup utility