In most situations Windows backup software won’t noticeably slow down your computer. If you are backing up to more than one device or multiple different destinations, or if you are backing up very large data sets, then you may notice your system slow down as it performs the backup. Otherwise, Windows backup software typically runs in the background or during dead time so you shouldn’t notice a decrease in performance. Also, it's a good idea, if the option is available with your software, to run a continuous backup. This will cause the software to perform backups of only the files you change in real time and it requires less bandwidth and processor resources to maintain.