In what way is it now very fast? Is it not very fast in playing games? Is it not very fast in booting windows? Is it unresponsive while on the windows desktop? Does it happen randomly or in certain applications? Does it only happen when running lots of applications at the same time?
All of the above is not an adequate answer as the pc given the stats you gave should fill the following.
Able to run windows with generally a small amount of lag when opening programs.
Able to surf the web while having multiple tabs open given a fast enough internet connection.
Able to play casual games without issue but slow down considerably when running high end games probably almost to a crawl.
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