msconfig is quite useful and provided you err on the side of caution can certainly help.
http://netsquirrel.co...nfig/msconfig_xp.html
Some programs have a mind of their own and insist on put an entry back in the startup folder every time start them up (hotmail and windows mail come to mind). Start the programs your Aunt uses and look through the options and 'untick' any applicable boxes to start at next boot, then click apply and okay, then close the programs down.
Obviously you need to let anti virus and firewall enabled in msconfig.
Another item to consider is when was the lat time a 'defrag' was carried out? I you do need to carry out a 'defrag' in might take quite a while. You can speed it up a bit by running the pc in 'safe' mode but it can take hours dependant on the defragmentation.