Likely no replies because hardly anyone uses FS98. Unless you are running a really old operating system FS98 may give multiple issues.
Looking at your specs, forget FSX, you really need a high end machine especially if you start throwing some reasonable addons in there. I'd recommend FS9 as up to this moment it is still a fully functioning flight sim. Masses of addons, real weather can still be added for free although through and external program which slaughters the inbuilt system anyhow, AI traffic is available, basically anything and everything. Tonnes of freeware and payware out there and FS9 will pretty much run on any operating system. You can get it off eBay quite cheap these days.
If you really want to continue looking at FS98 or anything pre FS9 there are various forums you can explore for info on this site. I'd personally be running straight for FS9 in your situation. Best of luck!
Edit: Regarding Saitek, no idea with FS98 but FS9 should work perfectly as long as what you have supports the operating system you are using.