I would bet my money on just reinstalling the OS rather than purchasing a registry cleaner.
What particular part is slow? Internet? Opening Programs, booting? Any particular issue leading to the problem?
Try downloading Speccy
and then install the program. To post and publish a snapshot of your PC..
In the Menu bar, click File
-> Publish Snapshot.
> then Copy to Clipboard.
On your next reply, right-click on a empty space and click Paste
on reply box then click Post
List Last 10 Event Viewers, List Installed Programs and List Users, Partitions and Memory Size.
A notepad will open then copy-paste the report on your next reply.