When do you work on computer in between boot and shutdown? I think you mean five minutes.... but still that is ages.
Backup all your data and reformat HDD, reinstall windows XP, (don't use vista as your laptop may be underpowered)
1 GB Ram is enough for laptop. so it should not be starved of resources.
I used Norton, Macafee, AVG. Found that Avast performs better than all of them so using it.First three Antivirus are CPU and memory hogger and slows down computer considerably. Avast seems to be ok so far. If you connect to internet or use external floppy or download programme or install, reinstall softwares often, then antivirus is a must to keep safety.You will never know what hit you once virus eats your HDD and computer won't boot. If you are always net connected then data stealing may also take place. There is no 100% guarantee but you can reasonably feel secure.
Spybot is a good programme but don't use it in tray, run once in a week.
You can read first post and follow some of the instructions found there, Boot performance increases considerably after using BOOTVIS.
pk