I did not yet try to restore backup of wallet.dat. its in my home pc.
I dumped privkey and imported it here, then I also imported privkeys of the purchased syscoins. nothing appears.
That's why mate. When you send coins it sends your change to a new address from the keypool, which is part of your original wallet.dat.
but I dumped privkey of my wallet and imported it to new wallet.dat.
but I dumped the privkey of the wallet in "receive" tab. does that mean the change is sent to "" or 0 or 1 address? i should have dumpprivkey "" ?
Once you start making transactions, your coins are no longer necessarily associated with your original private key. This isn't something the devs put in, this is something in all coins, including bitcoin.
When you sent that 100 coins, the rest of your coins also got sent to a new address in your wallet. The wallet in your home PC. That address isn't listed anywhere in the client itself (again, that's standard in all coins), it's attached to the wallet itself. You aren't meant to shuffle private keys around, because they're so sensitive. Best to move encrypted wallets around.
At any rate, your coins are fine, but they're on your home pc now. You can't get to them from anywhere else unless you move a copy of your wallet.dat file.
If, when you get home, you do want to see what addresses your coins are stored in, I suggest either going into options and enabling coincontrol and looking at inputs on the send tab, or going into help->debug console and typing 'listunspent'