Asp.net Web Forms Jquery using standard Drop Down List and file upload

Hello, I have a page where I'm populating another drop down list based on previous drop down list selection - I want to use Javascript to populate the drop downlists instead of reposting the entire page. I'm doing the same thing for FileUpload control on the same page. I'm uploading and saving the file to my server, when the file is uploaded I have an image that shows the image that I just uploaded and a "delete" button that becomes enabled so I can delete that image and upload a new one if I want. Everything works fine but the page is posting back, I simply want to use JQuery to get it working seamlessly as Asp.net Ajax doesn't work with the standard FileUpload and it's very inconsistent on with the drop down list (I think because I'm using Google Maps on the same page. I would rather have something more stable and I'm thinking that Jquery is the way to go. I'm writing this in Asp.net/VB.net and again I want to dynamically populate some drop down lists without reposting and also upload a file, save it, show the file and enable a delete button. When I press that delete button I will delete the file that I just uploaded and change the image back to a default image - using Jquery if possible.