Here's the system requirements - as listed on the Windows web-site...
1 gigahertz (GHz) or faster 32-bit (x86) or 64-bit (x64) processor
1 gigabyte (GB) RAM (32-bit) or 2 GB RAM (64-bit)
16 GB available hard disk space (32-bit) or 20 GB (64-bit)
DirectX 9 graphics device with WDDM 1.0 or higher driver
Therefore, your processor should be more than adequate to run Windows 7 - assuming you have the required disk space, RAM and graphics capabilities.
There are version of Intel Pentium one through four as well as Intel Pentium Pro, Intel Pentium D, Intel Pentium M, Pentium (2009), and Pentium Duel Core.
Yes.
None. Any processor written for Intel-compatible processors, from MS-DOS to Windows 98 to Windows Vista to Linux to Solaris 10 can be run on a Pentium D.
Intel 8088 Intel 8086 Intel 286 Intel 386 Intel 486 Intel Pentium Intel Pentium II Intel Pentium III Intel Pentium IV Intel Itanium Motorola 6800 Zilog Z80
There is probably no need to reinstall Windows after a processor upgrade, and the performance increase between the two said processors is probably not worth purchasing a newer version of Windows for.
The Intel Pentium Dual-Core is much faster.
No. The Pentium predates the Pentium D by more than a decade.
Yes.
On the contrary
No, you cannot.
Windows XP runs on any x86-compatible processor starting with the Intel Pentium.
windows 7,, but for me.. xp is the best! :D