If you look in winuser.h, you'll see the ALTTABINFO declaration is wrapped in an #if (WINVER >= 0x0500) block. You'll need to #define WINVER 0x0500 before your #include statements. --Mike-- http://home.inreach.com/mdunn/ The Signature, back by popular demand: Buffy. Pajamas.

Looks like you've got heap corruption - something has overwritten the start or end of an allocation block. A trivial example is:- char *ptr; ptr = (char *)malloc(strlen(origString)); if (ptr != NULL) strcpy(ptr, origString); // at this point you've overwritten the first byte // after the end of the allocated block at 'ptr' // this is because strcpy writes a zero byte at the // end of the string. Now this probably isn't the problem (the strcpy thing above) but can give you an idea of what is wrong. Alternatively a bad heap handle could have been passed to HeapValidate (which will call RtlValidateHeap). Stephen Kellett