XMPie has published a recommended list of server maintenance tasks here:
Bear in mind that it is designed for the latest version, so it mentions things that will not be there in the old v9 that you have.
1. run the windows "disk cleanup" tool to delete any windows temp files and old windows update files.
2. Then your first "xmpie" thing is to get into the dashboard, and delete any old campaigns and accounts that are not used or needed any more. This will delete the documents, images and fonts and print output files that are eating up your hard disk space.
2. Once you have just the campaigns/accounts that you need today, move to the job center and delete any old jobs - for exmaple delete any > 30 days old. - If you have many campaigns, this will take you some time, but persist with it. There are some tools in the latest versions that can help with this, but on v9, it is either a manual process, or write something using the uProduce APIs.
Those three things will free up your disk space. Once you have done that, do some more generic windows performance tasks like defragmenting the HDD, running SQL reindexing and compacting as described in the server maintenance technote.