If you want to make one yourself, the skills you need is being able to paste images to the screen (most of the time with some text on them) and mouse input. I made a GUI that I use in my games and, let me tell you, it wasn't easy. A GUI ranges from the simple "clicking on buttons" to text editing (sounds easy, but it's not). I went all out with mine: buttons, radios, lists, dropdowns, free text boxes, horizontal sliders, and a file system. It’s likely you don’t want all that.
Is it a 2D or 3D game? If you have a 3D game, you will want to be sure you know how to manipulate objects in 3D with the mouse.
At any rate, you will likely need buttons and lists for even the simplest level editor. Most GUIs have a grouping system for the selectable objects in a particular menu—I call them “menu groups”. Each group has its own buttons/lists/whatever associated with it so that when that group is being shown then will be rendered and checked for state changes automatically. There is really no good tutorial that I have found, so I was forced to make my GUI by imagining what I wanted each thing to do and then figuring out how to make it happen. It’s not much different than any type of programming; you just need to imagine it and convert your imagination into code…. I hope this helps you get what you are looking for.
I am pretty sure it has to do something with the float values being 'messed up' when they are so small.
Float values do have inherent error involved when they are VERY big or VERY small. The values you showed were neither. Sorry I don't know OpenGL. Where are you getting PCFreq? Is it part of the performance counter? If so, then it should take into account the PC/OS specific values for the clock. Do a check with both PCs. Have your program display the "time between frames". The TBF should be the same on both machines if the PCFreq is the same (or close). If you are running at 60fps on both machines then the TBF should always show ~16.6666666667 (on average). You will most likely see this number fluctuate between 16-17 depending on processor load.
Do you have a fixed vsync? If your desktop is higher end, then make sure you're not running at 120fps. You probably already checked this, but if your delta is higher on your desktop than on your laptop, then there is some inconsistancy other than the speed difference of the processors. Clocks are clocks and (whithin reason) they all click at 1ms intervals. Look at CLOCKS_PER_SEC to be sure.
On second thought, what ARE you using to get your Delta?
Write it into your code using obscure variable names. Don't put it into a resource file and the majority of people won't be able to change it or even find it until your program lets them. No safe is actually safe-- which kinda makes the word "safe" an oxymoron. Don't worry about the few people out there that will hack/exploit your game. The people that want to have a rich and full gaming experience won't look too hard behind the curtain anyway.
So, to sum up, JTippetts is correct. Don't worry about it-- you'll just waste valuable development time.