Have been Microsoft support for ten years of Windows XP is gradually near the end, a recent from the Czech avast!!!!! Security report shows, the vast majority of infected with malicious software Windows
XP users, especially the Rootkit program for XP, and 74% for Windows 7 is only 12%, and the market rate is compared lags behind, Windows 7 really in safety visible progress on, but with the malicious software of the author’s "upgrade", the latter number may be increased significantly.
Rootkit is usually some hidden in the parts of the system is not easy to find, to remove the malicious Rootkit program usually is very difficult, need some special tools to achieve, for example the boot sector scanning tools, etc.
At present Avast!!!!! The user has still a third in the old XP SP2 ‘most users don’t systems, to upgrade the reason is the Microsoft SP3 anti-piracy measures and WGA authentication.
Note that the 64-bit version of Windows in the Rootkit is little infection.