So it shows the Dell splash screen and then a blank. You can do a couple things first before calling dell help & support. Listen to your case, if you know a little about computers, try to listen for a clicking sound. That could be your harddrive dying (click of death). Also, what type of hdd do you have and did it COME with the pc, or did you buy it? Is it compatible with your system or did you have to buy a controller (card/adapter) to make it work? If it is restarting itself, does it EVER give you a blue screen with an error and parameters? (hexidecimal numbers) If so, this may be a conflict with hardware or your bios which you may or may not need to update. There are a ton of things you can try, but here...try sticking in your windows reinstallation disk (the disk that has your OS on it that Dell sent you or you bought). After that, turn your pc on and SPAM F2 for your setup (or F12 to just skip to boot order). Scroll down to boot order and hit enter. Use + and - to move the boot order to "boot from cd-rom" first. See if you are able to boot from that disk and maybe try a repair. The only other thing I would try first would be to SPAM F8 and try to boot in safe mode. If it starts, I would try to do a disk check (double click My Computer, right click your hdd [usually c:/] and click tools, under error-checking, click Check Now). If it pops up with nasty stuff, I would call Dell (since they don't like you adding hardware yourself) and either have them service it if it's still under warranty, or buy a new HDD. If none of these work, then I would reccommend going to CompUSA and buying what's called an "external hdd enclosure" (generally around 30-50$). Before you do this though, open your case, take out your hdd, and see what type of hdd you have (i.e. IDE, SATA, etc) so you can buy the right type. Head to a friend's house and follow the instructions. I hope this basic testing works. If not, *giggles* you STILL have Dell support lol.
some experience testing my stuff when it goes bad. hope it helps ^_^