iphone ios 4.0.2 wont jailbreak w/redsnow help!?

[Jeffery!]

Well i jailbroke my iphone a while back using my laptop and everything was fine until i accidentally deleted cydia packager and now cydia is gone! But that my laptop got stolden so i had to do it on an old 200 xp computer, so i browse for my 4.0 ispw file and it recognizes it fine, but when i go to put it in dfu mode it dosent work! all that happens is the apple logo appears for the first 3 seconds than dissaperars and nothing happens... Please help ill give you 10 points if you can help me, ohh and im using a generic usb cord if thaqt has any help