You wil have to do a manual reinstall, including reformatting the "C" drive then the manual install.  By installing an OS other than the original OS that came with the PC the Dell recovery is no longer valid.   If you do not have the Dell Vista install disc and the drivers and utilities discs, you will have to contact Dell for your country and try to get the discs.  If you can't get the Vista disc you will have to buy one.  You can download any needed drivers from the Dell downloads   www.support.dell.com       HERE is the Dell manual install instructions. 
i used to be able to restore it back to factory image. i have windows vista home premium genuine. but a couple weeks ago my friend told me that he can install windows 7 in my laptop and so he did. without know that he has the illegal windows and so now the not genuine windows its popping out and its getting kind of annoying so i tried to do a recovery by pressing f8 but then the factory image isnt there anymore i tried doing it manually from drive d: but then it freezgnizees in the middle and giving me an error without any message in it. i downloaded the WAIK and installed it tried doing using the command prompt ..i did the d:\dell\image\factory.wim and after that type the imagex /apply thing but it keeps saying that imagex is not recognized. can somebody please help me to fix this.. i didnt touch drive D: btw ever since my friend installed the windows 7 so i think the file is ok. been looking for a way to fix for 2 days. pls give me a correct stepbystep tutorial since im not really good with os or cmd.. all i want is just get my genuine windows back.. anyway to do this.. was thinking of installing back windows vista home premium.. but it would be nice if i can do it by using the factory image thanks in advance
factory image restore freeze with blank error