I discovered that some of the posted download doesn't packed with all the respective drivers (only Mdmchipv.INF file), although some claims that they do!!
If you are using PCtel PCI HSP 56kFlex V.90 modem this is guaranteed to work for you (for notebook-eg. ASUStek and Desktop).
*If you need help on installation, e-mail me
Try it then thank me ^_^