Replacement chainring compatibility I have a Fuji Absolute 3.0 (about 2011) with a generic crankset. The triple chainrings are stamped with 'SAMOX'. It is a 30-42-52t set. I favour the middle chainring, which is now badly worn and needs to be replaced. I have also recently replaced the chain and cassette (8 speed).

The teeth on the largest and smallest ring are in relatively good order, and I have a tight budget, so my preference is to change only the middle ring. However, I can't find any SAMOX parts or any details about the compatibility, and I don't know anything about chainring specifications, bolt layouts, etc.

My other option is to replace the entire crankset and bottom bracket (there are occasional creaks and bangs, so it might be time to do so), but then I face not only the cost, but also ensuring the crankset will match the other components.

Does anyone know whether a Shimano or other 42t chainring will fit this configuration?
You can use another brand's chainring just fine, provided that the chainrings are replaceable (some cheaper cranksets are made such that all the chainrings are made in one piece). Assuming that is the case, you just need to measure the B.C.D. as shown here, find a chainring with the same BCD and number of bolts and number of teeth and bolt it on (there is a table of common sizes there).  

Based on the bikes direct picture, it looks like it uses 104 mm 4 bolt chainrings, but thats the current version (so check it out yourself) - do the measurement with a ruler as shown in the prior link. EDIT: This may be a different bike - several different models come up on google for the same bike name. Do the measurement with the ruler. 

Here are some directions on replacing the chainring. Note that you may need some tools you don't have (but for the big ring, you might be able to get away without removing the crank) to remove the crank (namely a crank puller; in a pinch you could use a mallet but I wouldn't recommend it).  

Park Tool also has some nice directions on removing and reinstalling the crank, which you'll need to do in this case since its the middle ring. 

Also, wearing out a chainring in 3 years is pretty quick for most people who ride a hybrid - chainrings typically last more than 20000 miles in my experience, even with cheap ones. I also wouldn't bother replacing it until it was causing problems.