I have a Windows XP SP-2 system with 512 MB DDR-1 RAM installed. Can I upgrade to Windows 7 with this amount of ram? This PC is for general purpose computing like net surfing, MS Office apps, VOIP chatting and maybe an occasional movie video. I am not inclined to upgrade the RAM since this is an old system and DDR-1 RAM is more expensive than DDR-2 RAM.