Desktop processors can be changed. However, some laptops can have there processor changed, some cant.
There are many versions of the HP Pavilion desktop, some versions have Intel i5 and i7 Processors and some have AMD Athlon X2 to AMD Phenom Processors.
heat-pipe
an ice pack
A cooler.
There is two types. There is DDR notebook RAM and there is DDR desktop ram. They can't be used vin each other (notebook RAM can't be used in a desktop) unless (in rare circumstances) you happen to have a notebook ram port on your desktop's motherboard. But no, DDR is a technology. Both desktops and notebooks support this technology because there is notebook DDR and desktop DDR. but notebook DDR can't be put in desktop DDR and vice versa.
Yes of course it has no differnece the same things work on a desktop or notebook same technology used.
A fan and a heat pipe.
Mobile Desktop
notebook IDE connector= 44-pins Desktop IDE connector= 40-pins
Yes.
300$ - 600$
Almost all CPUs that have been used in personal computers since 1981 have been capable of supporting a desktop environment of some sort. This includes the Intel 8088 and descendants, the Motorola 68000, SPARC processors, PowerPC processors, ARM processors, Itanium processors, and Alpha processors. There are hundreds of models within each family, making a list of all of the ones that could support a desktop environment implausible.