Windows is very slow, often unresponsive, and will not update

hi everyone,

Ok, I turned on my computer last week after it working fine and it all the sudden became very slow and unresponsive to the point of no use. So i reinstalled windows using the recovery partition. After reinstalling windows my computer is still very slow, often becomes unresponsive, windows updates will not download or take absolutely a lifetime to download. I am at a point where i do not know what to do. It is mid semester in school and this computer is important. Any help what so ever would be great. Thanks everyone

What does Task Manager say? Are there any processes using up 90-100% of CPU e.g. an Antivirus product or possibly a malware infection. What is is the specification of the PC? Also, I would check that the ADSL Modem/Router is working ok, try accessing the device via its web interface to see that its working ok.