I had Win7 on my laptop (technically still do) and I installed Ubuntu 13.10 on an unused portion of the drive. Ubuntu started up OK, but didn't work well with my wireless at work. So I tried to boot back into Windows and it won't load the bootloader. If I select the SYSTEM part (which contains a loader) it does nothing. If I select to boot from the part I know has the copy of Windows it fails with a C000000F error (File not found). I tried to repair the boot manager using the win7 dvd, but now not even GIMP is showing up. I know I can get GRUB to work again, but I think I have to repair the windows boot loader first. I'm not sure how to do that.
I know this should probably go in an "Ask Win7" SE, but I don't know of one. So if anyone can help me restore windows or point me to a good windows tech forum I'd appreciate it.
EDIT: Here's a little more technical detail. I have an HP laptop that came configured with four drives: SYSTEM, Main, HP_TOOLS, RECOVERY. SYSTEM is what it says it is. It's actually the boot drive that loads the operating system on Main. When I installed grub I put it on SYSTEM thinking that would cause the least amount of confusion to the core boot loader. However, I realized this was a mistake early when I tried to boot to that drive only for grub to reappear. I tried to boot into Main but that caused the 0xC000000F error. I can't find a log that tells me what is causing that error. I can (now) boot into Ubuntu just fine. Boot-Loader didn't detect a problem on any of the drives and it didn't fix anything.
RE-EDIT: I should also probably mention that these four drives used to each be primary partitions. I changed HP_TOOLS and RECOVERY to logical partitions. I'm not sure if this is important or not, but something I read somewhere made me think it could make a difference.