I am having problems with my computer. Help!!?

I was giving an old computer, it was used for a motel business. It is very slow and won't download without errors. I can't even download any antivirus for my computer. I have tried to even download an antivirus that I bought. It is always kicking me off of things. there are always errors. I've tried computer repair software, but, always end up with the same problems. This is why I want to change from Windows XP Pro. to Windows XP Home. Because I do not feel I need all the programs that it has on XP Pro. Of course I could be wrong. After all, I am computer illiterate. Why would I need all that comes with XP Pro? Just asking? What are the advantages? I don't own a business or anything that pertains to a business. So, convince me that I would be better off with XP Pro.