I have a Dell XPS420 with the original memory fitted, (Win 7 Pro 64)
2 off 1GB IRx8 PC2-5300u555-12-zz
I tried fitting two additional modules from an unused Dell Dimension 8400
2 off 1GB IRx8 PC2 4200u-444-12-zz
DDR2 533 CL4
Would not boot giving reason as Memory detected but Incompatible or Unconfigured
Grateful if anyone could let me know if memory is incompatible or if I need to tweak something.