Nope. The worst that would happen is that the card would fail to function properly. A 300 watt HP supply should handle all but the most greedy cards.
i have a 255 watt PS and it's running a radeon X600 and a pentium D.
how it's running them is beyond me, but whatever.
since this is sort of on the subject, it's a low profile system (a dell xps200), and i think the power supply was made so low to avoid overheating. i want to upgrade to an x1600pro (which seems to be the best low profile card available), but i'm worried it'd need more power (especially since the 600 is cooled by heatsinks, and the 1600s i've seen all have fans).
the low profile design doesn't leave much room. i'm worried that upgrading the power will create more heat, despite the fact that i'm sure dell used a very poor stock fan on the current PS. so that means i need new fans, but the only space is for an 85mm frontside intake fan. has anyone seen any 3.5 bay fans? my small bay is currently unused. stupid dell. i've seen PCI slot fans, but not for an LP design, and i've only got one PCI-e X1 slot to spare, which i was hoping to save for a TV card.
anyway, some advice would definately be appriciated.