Update Page Problem With Product ID

Hi

I am experiencing two problems with my update page. I set two file upload fields on my update page one for thumbnail images and one for full size images. However i later realised that i only needed the thumbnail image upload field so i deleted the other.

When i update a record in my database it overwrites the product ID and sets the product ID to '0'.

If i do any further updates on other records on the database i am directed to a blank page throwing up the error message;

"Notice: Undefined index: WA_UploadResult2 in C:\xampp\htdocs\Admin\products_Update.php on line 79
Duplicate entry '0' for key 'PRIMARY'"

I know the first part of the error message is relating to the full size image upload field that i deleted. The second part of the error message is in relation to my update page setting all my existing record product id's to '0'. I dont understand why each update is overwriting my product id's and setting them as '0'.

I have zipped up my update page and attached it could you please help me understand and resolve both these issues?

Thank You