Dell Memory Question

[arrowshooter]

My Mom has a Dell Dimension 4500S that is in bad need of a memory upgrade. Specs call for up to 2GB PC 2100 DDR SDRAM (non-ECC). I have in my hands 2-512MB stix that say PC2100 and PC2100R. If these turn out to be ECC instead of non ECC will they still work?

 

[muz]

ECC ram will not work in A non ECC motherboard
The stick you have that says PC2100R is registered which means its ecc ram
whereas the other stick should not be ECC as they are usually clearly labbeled as such , either with the R or a label like this

 

[arrowshooter]

Just what I was looking for. Thanks.