Add 2 GB more RAM. If you have 4 slots, get 2x1GB RAMs. If DDR2 RAM, is not readily available in shops then you can get it easily from shops dealing in used PCs, they have that at very reasonable prices with check warranty.
Corsair maybe expensive and hard to find, but you can get any other brand. RAMs do not get faulty in most cases, if you handle them properly.
2 GB RAM is just for basic use, you must have 3-4 GB RAM for smooth gaming.