OK, I'm guessing that by deleting, you mean that someone went into the BIOS and removed the HDD from detectable ATA Devices. If thats the case, go into the BIOS (Usually hold the del key during posting) then go into "Standard CMOS Features". Make sure that your Hard Disc Drive is listed there. If not, cycle through the options till you get to auto detect.
Save and exit.
If this doesn't work, then go back into the BIOS and select "Load Setup Defaults". This will hopefuly reset all the configuration Data in the bios to default values that should remedy any bios problems.
Note, this is for Award layout BIOS's, The menu options may be different with different BIOS's.
Anyway, If that don't work, It'll be the data on the Hard Drive thats causing the problems. It could be anything, you would need to try and locate the problem, therefore I recomend starting from scratch, repartion the HDD and do a fresh install of windows.