OK. Here's the problem. grub can't boot Windows directly. It needs to "chainload" the Windows bootloader in order to boot into Windows. The Windows bootloader normally lives in the MBR, but that's where grub now resides, so the Windows bootloader has effectively been clobbered. To get back into Windows u may want to take it in to a Windows tech. Once you're back in, with a little care, you can have another go at fixing grub.
Basically, for a dual boot Windows/Linux system, you've got two choices ;
1. Use the Windows bootloader to chainload grub. In this scenario, you install grub to one of your partitions, not to the MBR.
2. Take a backup of your MBR containing the Windows bootloader, install grub to your MBR, then chainload Windows by pointing grub to the MBR backup you took earlier. Involves placing the backup somewhere grub can access it. A good place is on the Linux /boot filesystem.
In the past, I've used both methods, but the 1st is by far the safest & easiest because you're leaving the MBR well alone. Two bootloaders must exist. Leave the MBR to the inflexible one.
Anyway, sorry I couldn't be of more help. At this stage, you'll want a Windows tech to get your Windows bootloader repaired. They need know nothing about Linux.