goombah,

I would have said to do a disc cleanup and defrag but you said you've already done that. The defrag usually speeds it up for me.

As for free malware, I recommend Malwarebytes. I've used it for years and it's free. You can update to the Premium version, which gives you real-time protection (it's $25 a year for 3-PCs). It used to be $20 for a lifetime subscription!

CNET

I still have Windows 7 and refuse to upgrade to Windows 8 (I've heard nothing but bad things about it). You could also try typing msconfig into the "Search Programs and Files" under the Run Dialog box (hit the Windows Start button and it'll be there on the bottom). This gives you the ability to determine which programs run when the computer boots up (you could have a lot that is slowing your system down if you're trying to open your Internet browser once the desktop is up).

I hope this helps!