Good evening,
I thought about a solution to find the last boot time stamp (in seconds) which should work
The only limitation is that on Win2003/XP and earlier it works if and only of the server
is not running for more than 47 days.
The trick is:

use a combination of GetTickCount(/GetTickCount64 to get the ms since last boot
Use GetSystemTime to get current system Time
Next, with some int64 magic, get the boot time by subtracting the elapsed boot time from current time
Next, go back to a SYSTEMTIME structure
As there are some different time functions involved, it seems that the ms part is no completely reliable, but the other members are

do you think it may work ?

here is a little sample:

#include    <windows.h>
#include    <stdio.h>

int main() {
    SYSTEMTIME    st;
    ULONGLONG    tk;
    ULONGLONG    now;
    FILETIME    ft;
    ULONGLONG    u_boot;
    FILETIME    ft_boot;
    SYSTEMTIME    st_boot;

    GetSystemTime(&st);        //current time
    tk =    GetTickCount();        //millisenconds since last boot

    SystemTimeToFileTime(&st,&ft);

    now = * ((ULONGLONG*) &ft);


    u_boot = (now / 10000 - tk) * 10000;


    //get a FILETIME back
    ft_boot        =    * ((FILETIME*) &u_boot);
    FileTimeToSystemTime(&ft_boot,&st_boot);


    printf("\nFunction Parameters");
    printf("\n\tTick Count             : %u",tk);
    printf("\n\tSystem Time to FileTime: %I64d", now);
    printf("\n\tBoot Time in 100ns     : %I64d", u_boot);

    printf("\nBoot Time Was   : %04d-%02d-%02d %02d:%02d:%02d.%03d", st_boot.wYear, st_boot.wMonth,st_boot.wDay, st_boot.wHour, st_boot.wMinute,st_boot.wSecond,st_boot.wMilliseconds);

}

Regards
L. Trivelli