|Have you tried cleaning up temporary files using the portable version of CCleaner?|
You can/should ignore the registry section of that program.
Is your hard drive a HDD (old type) or a SSD (new type)? If it's a SSD, you shouldn't try defragging it. If it's a HDD, after cleaning with CCleaner, try defragging with the portable version of Defraggler. It saves a lot of time and performs very well on Windows XP.
How exactly did you delete those Windows Updates? If they're considered critical updates, you should keep them installed. It sounds like you have Automatic Update enabled and so they were reinstalled back on.
Have you recently performed a full system scan (after updating all available definitions) with Malwarebytes and SuperAntispyware?
What is the total capacity of your hard drive, and how full does it say it is within My Computer?
Apologies if I don't respond to your reply immediately. I don't check this site daily, but you're welcome to PM me as a reminder.