There is nothing you can really do for N450 or any other early Atoms.
I had one of those netbooks with N450.
I tried every OS I had at that time incl. Linux Mint.
I also tried to replace the HDD with an SSD.
The processor is simply to weak. Nothing really helps to speed things up a bit on the netbook.
I gave up already a long time ago.
I would say, forget it! Do yourself a favor by buying a new PC/laptop with relative new i3 at the very least.