if you're running a Core 2 Duo on an Intel Motherboard, with a NVidia graphics card you are laughing.
If you're running an AMD machine or something without SSE3 it gets a little more involved.
Source: VMWare Knowledge Base If you have a jailbroken i Phone, you can install the iphone-gcc toolchain onto the i Phone through Cydia and that way you can just compilie the apps on the i Phone.
Apps that are developed this way can still be submitted to the App Store.
Is there any way to tinker with the i Phone SDK on a Windows machine?
Are there plans for an i Phone SDK version for Windows?
Apple does not allow these Client OSes to be virtualized.
Alternatively you could pickup a low-spec Mac Mini from e Bay.
If you don't want to purchase a mac you can either run OS X on a virtual machine on your windows box, or you can install OS X on your PC. The other option is to install OS X on your PC, commonly referred to as a hackintosh.
In my experience the virtual machine solution is unusably slow (on a core2 duo laptop with 2G ram). Hackintoshes work quite well - my friend just sold his mac because his Dell quad core hackintosh was actually much faster than the apple hardware (and cost about 1/3).
Also a lot of time they make you use Objective-C equivalent statements simply in another language.
They kind of look the same but there are always subtle differences that you have to learn on top of obj-c.