Can't sign into my User - Opening as Temporary user!

A few days ago I attempted to sign into my Dell Studio 15 - I had two user accounts - a Guest and my own area set to Admin. Straight away I noticed it was taking a long time to sign in and after a few minutes it had opened me onto a completely empty desktop, with all my files missing. At first I thought I had a virus of some sort and that my files had been wiped, but after hunting about and doing some digging realised that Vista had logged me onto a temporary user, and that all my files were hidden deep in the Windows/User section of my laptop.

After having a google to work out the problem, I created another Admin account and backed up all of my files onto an external drive - however, some of the hidden folders suggested to copy from my user area wouldn't copy over due to admin settings. I wasn't too worried about this as I was more worried about the actual data on my hard drive, which is now secure. My laptop doesn't have enough space remaining to copy all the files back on, so I was planning on deleting my old user, creating a new one and then copying everything back over (this would work, right?)

However, upon creating a new user area to store all my data, I realised that my system was running abnormally slow. Firefox literally skips to Not Responding every few minutes, won't let me update anything and my system is generally taking a good time longer to work. Every new webpage opened skips straight to non responding for a minute or two and I'm worried I have a virus/system issue of some sort. I've ran Malwarebytes to no avail, and am currently defragging the system to hopefully unclog it a little. I don't want to delete my original user yet/transfer all my files over for fear of my whole system dying. I've also never used the system restore function and am unsure how it would work in a scenario like this. Would it be that my hard drive itself has corrupted portions? Or just that a virus of some sort has wormed its way into my system?

Sorry if I seem fairly technology-illiterate, I'm not really too sure about what I'm doing. In a simple way, could any of you help and let me know what is best to do in this situation? I don't want my laptop to be out of action as I have no way of replacing it for a few months, and most of all I don't want to lose all of my files during transfer or in the near future from a complete system failure.