Windows IDE for Intel x86 Assembler?

MASM is an x86 assembler for Windows that uses the Intel syntax. (MASM Homepage)

For an IDE, you could use MASM with Visual Studio, as described here, or you could use something smaller like RadASM. WinASM is also another one.

When I do any ASM on my Linux box I use NASM plus a text editor (gedit).