Good…so my advice is fully relevant (I use Windows 7 as well).
It really sounds like you have stuff running in the background that’s clogging it all up. I usually make sure to have a purchased version of Windows that I can install…so my install is clean and free of junk many manufacturers put into their discs that they include.
I also will sometimes turn off the wifi. Once had my computer lagging, only to find out it was trying to download updates behind my back, as well as syncing my Dropbox. That stuff can be done when you’re not DJing.
Beyond that…running Traktor (or in your case Serato) as an Administrator and keeping a clean system will do you fine. In reality, you’re running your laptop the way a Mac works. No bloatware, no unnecessary junk.
Let me know how it all works out.