Hello and welcome to the forum.
1 month doesn't seem like a lot of time, but I suppose it depends on a lot of variables, like what you've installed during that time either intentionally or perhaps unintentionally.
Check the msconfig startup tab by typing msconfig after clicking the start orb and inspect what's there. Too many apps or unnecessary services starting at boot time can impact system performance overall.
Another method is to launch the System Information utility
type msinfo32 into the search box after clicking the Start Orb
Expand Software Environment and select Startup Programs.
If you suspect a possible infection then you can grab a blank CD and this program
What is Windows Defender Offline? (get the correct version...