i installed Fedora Core 4 on a Linux partition and it runs fine but when i try to boot windows the computer shows the error message "autochk program not found skipping autochek" and then it reboots!

u will have to run the fixmbr utility from your win XP cd to get back win

also have atleast one partition between win and linux

No, don't do that - at least not yet.
Anaconda (or whatever the installer is called these days) probably guessed the Windows partition wrong.
piuman boot to FC4 and post the output from the following "fdisk -l" (that's ell as in list). Also post the bootloader config file - probably /boot/grub/menu.lst (maybe grub.conf).

piuman: Did you create the ext3 partition(s) with PartitionMagic?

If Yes, then the windows partition is likely hidden and needs to be changed to a “unhidden” type using linux fdisk before windows will boot.

piuman,

WhatsHisName is right. If you used Partition Magic 8 to create your partitions, it added a registration key to your windows registry. If, when you are trying to access XP, it throws that error, try to boot into Windows in safe mode.
When I got that message and booted in safe mode, it listed a number of files it was trying to locate, and all were listed like this, or similar:

(0)partition1(0)windows(0)XPHome(0)xxx.dll

What I did was boot to Linux, and run fdisk -l in the terminal. It showed my XP partition as hidden. I then rebooted the machine, and at the GRUB splash page, went into the edit GRUB settings (the paragraph under the OS listing has instructions on what keys to enter for what functions) and I added 2 lines to the existing:

Before
rootnoverify (hd0,0)
**something else**

I added:
unhide (hd0,0)
rootnoverify (hd0,0)
makeactive
**something else**

Then I saved the changes, and Windows booted right up. When I had the same problem on my desktop 6 months ago, I made the mistake of running fixmbr from XP's Advanced Recovery Console, and it really messed up my XP installation. It didn't recognize much of the partition and I lost alot of work I hadn't backed up. Had I known then that the "fix" was this easy, things would have been much easier on me, but like they say...live and learn.