Need help securing / streamlining old laptop

I've got an old Acer Aspire One that I just got done scanning and fixing the whiz out of, and I'd like some recommendations for firewall and anti-whatever-ware stuff to keep it falling prey to attacks on WinXPSP3.
I can provide more system specs if needed.

I'm sure it could also use some sprucing up to get it to work smoother and faster. It's already double the memory (2GB) of when I first got it, and it seems slower / more problematic than I remember.

Belarc advisor lists a lot of security updates missing, and "updates are ready for my computer" after all the network stuff got fixed and a lot of default system settings were restored. I'm assuming I should install whatever pending windows Updates are there.


Thanks for any advice.

 

For security:
1. Avast! Antivirus.
http://www.majorgeeks.com/files/details/avast_free_edition.html

2. Malwarebytes Anti-Malware.
http://www.majorgeeks.com/files/details/malwarebytes_anti_malware.html

3. Privatefirewall.
http://www.majorgeeks.com/files/details/privatefirewall.html

For performance:
Nothing beats a fresh install - if you have the Windows CD and all the programs' setup files.

Other than that, clean and defragment the hard disc with:
1. CCleaner.
http://www.majorgeeks.com/files/details/ccleaner_standard.html

2. Defraggler.
http://www.majorgeeks.com/files/details/defraggler.html

All these programs are free.