I think it should work. Low End Mac says here that the 1.42 uses PC2700 RAM. If you use that or faster RAM, I would think you could use a 1 Gig stick. However, I personally wouldn't buy 1 gig DIMMs, because they're about 4 times the cost of 512s.
According to the hardware specs, 1GB memory modules should work, however, you are still limited to 2GB on the Dual 1.42 - You may was well just buy the 512MB memory and save yourself some money.
According to the hardware specs, 1GB memory modules should work, however, you are still limited to 2GB on the Dual 1.42 - You may was well just buy the 512MB memory and save yourself some money.