Considering how slow your system is, some games may run faster with VGS... just make sure you get the Windows XP patch. You should still try ePSXe first.
Windows XP will usually run slower than 98 on a a 350mhz PC... although P4 systems run better with XP. Anyway, you should be able to run some PSX games working (with serious frameskip) with either VGS or ePSXe. I think you might be getting that WNASPI32.DLL error with ePSXe... just read the notes that come with the CDR plugin on how to configure it for your CD-ROM with Windows XP.
