I bought a used pc and wish to perform a clean install (format the hard drive) Would I need a boot cd or will it read the xp OP disk upon system boot? Also….a used computer is registered in someone elses name, can an op be reregistered into the current owners name?

i only have 40Gig hard drive capacity where i make 30:10 partition. driveC has 30 where i already utilized 85% of the spaced. although i always do disk clean-up, i still think that i do not get the enough clean-up. specially when i see scan files over 260000. are there any other way to reduce the system files. can we delete some files direct from the windows folder.

Compaq presario 5000 desktop series my hard drive is 20GB SDRAM 128MB CPU intel Celeron 800MHz Bus speed 100MHz, windows 98 DC rom. HOW to speed it up windows 98. will Registry Cleaner work

i was just wondering how i can check that there is no bad stuff stored on my computer and how i can clean up my hard drive so there is more space on my hard drive and not any unwanted files.

also

what files that are already stored on my pc are ok to delete?

I have a Windows XP Professional With 74GB Hard drive. I need to know how to clean my computer more effictively. Can you tell me how? Thanks!!!
please tell me what to do with my computer to make it faster too i will accept all answers cause this is slow.