uploading files to our server has never been a problem with us. in our part we let users upload jpg,gif and flash files to our server. what you basically need is an upload component. if you are using ASP as your server-side script, ASPupload is quite suitable. that's what we use anyway, and it hasnt given me any problems. the downside to this is of course, you have to purchase it. there are other upload components there, though a very few of them are free. each components has its own way of letting you specify where to put it in your server. some even lets you rename it.
hope this helps.
biggie