Dell Mini ~ OS Not Found?

Hi guys! I have a Dell Mini, and about 6 months ago it began running s-l-o-w because there wasn't enough remaining memory. I had it wiped clean and the operating system reinstalled. When I would turn it on, it would list both operating systems and I would choose the new one and it would start up just fine. It has been working no problems until recently when I went to turn it on and accidentally chose the wrong operating system option… now it tries to boot up and just says "operating system not found." When I turn it on now it no longer gives me the option to choose which operating system to use. How do I get back to where I am able to choose that?

who wiped it clean and reinstalled the operating system for you?? you should never of had a choice of which operating system to start up if they had done things correctly in my opinion.. anyway i think the best easiest option now is to do a repair install which should fix your problem with the bootloader and mbr.

Not sure but maybe repairing windows can help you to fix this problem.