I found out how to get the HDD space and the available:
Code:
main()
{
    long var;
    struct dfree *df;
    getdfree(3,df);   /* drive #3 (C:\) */
    var = df->dw_avail * df->dw_sclus * df->dw_bsec;
    printf("You have %ld KBytes left on your Hard Disk", var);
}
If these functions look wierd(ie. getdfree(), It's because I used PowerC by Mix.

Now, can someone know how to find this info out on system memory?????