The Xbox One has a built in Blu-Ray/DVD player for movies and streaming apps like Netflix, Hulu Plus, etc. I think that they have their own digital video store as well. If you mean transferring movies from computer to console by means of USB, Microsoft says that USB transfer is not available at this time during and after launch but will be soon. They may have been talking about USB streaming for music but I can't be certain. It will support 1080p games but that depends on the developer and the type of television that you have. FYI, you should know that Call of Duty: Ghosts only shows 720p resolution. For what reason, I don't know because PS4 supports 1080p.
Microsoft claims that hard drive is non-replaceable but there is a teardown method on this site that shows that it is more replaceable than they claimed. However, it require the user open the console completely which voids the warranty and I'm sure that the console won't work correctly if it is replaced so I wouldn't take any chances trying to do so. PS4's hard drive replacement is a lot more user friendly. All you have to is slide out the shiny black part on top of the PS4 and unscrew a couple of screws and slide the old hard drive out. Also, be sure to have the new PS4 firmware on a flash drive to load into the console so that it will work as soon as you reboot it. This process takes about 5 minutes depending on internet speed. Hope this helps.
If it was me, I would replace the hard drive all together and reinstall Windows on a new hard drive and format the old drive. You will lose everything unless you already had it backed up though. However, if Dell makes has a recovery disc for your computer brand and model, you should order it and give it a try but you will still risk losing everything. Another method is to download a free anti virus program and a disk cleaner for junk files. I use Avast for anti virus and CCleaner (Spelled as it is shown) for junk files. Not sure if these good fixes but it is worth a shot, however, reformatting the HDD and reinstalling the OS are the best choices if you want a long term fix because I know that computer techs use this method all the time. Anyway, I hope this works out for you.