To improve the security of my sites I therefore always disable the default administrator url, and also monitor all attempts to access the default admin login url's. For Joomla sites you could e.g. use the extension called Adminexile which will notify you by email of any attempt, and also dynamically ban perpetrators for a timelimited period.
By doing so, you can monitor all such hacker attempts and take further measurements should they be persistent.
Microsoft Windows Xp coming to an end
It is important to remember that support and updates for Microsoft Windows XP comes to an end on 8. April 2014.
In one case where I wanted to keep an old PC I got, I decided to spend €60 on Windows 8 Professional to keep this alive. In other cases I have installed the "Windows like" Linux Mint.
If you go for Linux Mint, then be sure to download and create a bootable DVD first to ensure that your hardware is compatible. I have self several times experienced problems with the Broadcom wifi modules installed in some laptops.
Either way, I will recommend that you make up your mind wrt. this as soon as possible as staying on Windows XP is not really worth it.