Regardless of why you want to reverse your two weeks notice, asking to stay in a position from which you have resigned can be difficult. Your company may have a policy about this issue. If so, that policy will have to guide you through the process. If there is no policy, both human resources and your direct supervisor will be the primary decision-makers in allowing you to stay in the position. Because your initial resignation may have caused some emotional ripples in your department, remain as professional as possible throughout the entire process.
Write a letter formally asking to withdraw your resignation. Do not apologize more than once or twice in the letter. Be brief and professional. This letter will likely be in your employment file. Print three copies: one each for human resources, your supervisor and yourself.
Speak with someone in human resources. Large companies may have encountered this issue in the past and may have a policy about such circumstances. Bring a copy of the withdrawal letter with you and present it to human resources. You may find human resources will focus on the the broad policies and procedures and less on the details of your return.
Speak with your direct supervisor. Have a copy of the letter with you for this meeting as well. Expect this meeting to be more focused on the reasons for the initial resignation, the reasons for your change of mind and the impact on your department and/or the company as a whole.
Be honest, but brief. Focus on what your current job offers for professional opportunities and why you would like to continue to pursue those avenues. Express what you can still bring to the department.
Ask for the job as a yes or no question. "Can I stay in this job?" Simple, clear questions are easier to answer with an affirmative.