Booting-up freezes and run so slow on my Windows XP Machine

What would be the reason why laptop boot-up and run so slow? Can someone out there elaborate me all the possible cause why my laptop boot-up and run slow? Does it have something to do with the computer specification? It took almost 1 minute before it completes the boot-up process.
My laptop also lags most of the time and sometime freezes for a couple of minutes. I scan it with an antivirus scanner but no viruses have been detected. It was almost a month since I’ve never reformat my computer maybe it is the cause but there are some programs that I need and I don’t have any backup. Is there any other way to solve this problem, please tell me what to do? I’m using windows 7 starter as my operating system, if ever I reformat and downgrade my operating system to XP would it help my laptop work faster.
Here is my computer specification.
PROCESSOR: AMD Athlon ™ II Dual-Core M320 2.10 GHz
RAM: 2.0 GB
DISPLAY ADAPTER: AMD with ATI Mobility Radeon HD 4200
