The question is:
In a couple of days im gonna buy new PC, so will I be able to play crysis 2 on another PC with old harddrive?

Yeah..question is since the HDD is the most bottle necking component of a PC why would you not get a new one?

The old, i mean my current 1Tb Wd harddrive. I just dont want install the game right now, play, and buy new copy of crysis, just because i bought new PC.

You can activate the game on up to 5 different PCs.
Deinstall gives you one activation back and you can order more by asking EA support should you exceed that limit

So no, you don't have to buy a new copy of Crysis 2