"Will I be able to run Mac OS X on my Dell?
No.
"We will not allow running Mac OS X on anything other than an Apple Mac." - Phil Schiller
Granted, many users have reported that they got Mac OS X to run on their PC, using developer copies of Mac OS X. However, this can be very problematic and it is not permitted by Apple. When x86 Macs start coming to market, it is likely that there will be some sort of digital rights management to keep Mac OS X from running on non-Apple machines.
and...
Will Macs switching to Intel processors mean viruses will be coming to Mac?
No. The insecurity of Windows is what causes the propagation of viruses. For instance, Mac OS X user accounts don't run with root privileges as in Windows. Windows also ships with a lot of ports open by default, while Mac OS X ships with none. However, while the design of the x86 architecture is, theoretically, more vulnerable to buffer overflow attacks, this is still mostly dependent on the software allowing such attacks to be executed.
Furthermore, there are many operating systems already running on Intel PC's that see no viruses. Linux, for example, is a very popular alternative operating system that has seen almost no viruses because it has been designed to be secure, just like Mac OS X.
In short, your Mac will still be a Mac. It's just going to contain components made by a different company."
this information came from...
http://guides.macrumors.com/Mac_OS_X_on_Intel_FAQ