Computer/Downloads hanging

Hey all didnt really know where to post this but this seems pretty general place to post so here goes ill list my specs:
Nvidia P532-E SLI MOBO
Geforce GTS 450 vid card
2 gigs of crosair ddr2 ram
1 TB western digital HD
windows 7 home premium x64 edition

I was previously running windows xp 64 edition with a lesser hard drive. I wanted to upgrade because it was time so i just recently put the new hard drive in and installed windows on it. Something went wrong with the windows install the first time so i did another fresh install. Everything seemed to be installed correctly the 2nd time but the PC was hanging a lot without really doing anything. I did another fresh install and this time seemed to be the charm. Everything is up to date and fresh. I went to download world of warcraft and everything is fine until i get to the update portion on the launcher for blizzard. Its prob. 75% done and then it starts having issues most of the time when i restart the download it will ramp up to an ungodly speed and then maybe go for awhile at 400 kb/s but eventually dropping to 0 kb/s and not moving. ive tried to let it sit and see if it will go again but not luck. Same thing happens when i try to download the game file for League of Legends ive got it to get to 99% by starting and stopping the download but after 10 seconds or less of it starting again my computer freezes randomly and the program wants to crash or the download hangs like the other mentioned about. I have downloaded steam and CS:S completely. I am just really lost and frustrated. I did purchase 8 gigs of corsair ram that wont be delivered for a week. I am just looking for a solution or an explanation on what is going on. Thanks in advance if you have anything for me.