|And you wish to remove XP and install '98SE?|
Presuming so.. The RAM isn't an isue - you're obviously under the '98 limit of 512 Meg (thus no need of tweaking ini files).
In truth you have more than enuff RAM for '9x/ME to wrk very happily... Any more is a waste - unless you're into serious number crunching apps (spreadsheets and serious games etc....).
Boot up with a '98 bootdisk - the one with the later Fdisk inculded; or even better an ME to bootdisk to same end (and that it also available at bootdisk.com as a download - and probably better to get that one anyway regardless)
Run Fdisk and inspect partitions; then opt to delete the non-dos partition (which is how dos/'9x/ME see ntfs...)'
Then (still using Fdisk) reconfigure the drive afresh... I suggest a decent size Primary for the OS etc.... and balance of drive (Extended partition/logical-drive) for data - only... I'd suggest 5Gig for OS etc; certainly no more than 10Gig...; as '9x/ME don't need much room (unless you really stack up assorted apps/utils etc....).
Format both as fat32.
Then with the '98 CD in the slot/drive... access it and run '98 setup routine; install it to c: drive...
You may have to find the graphic card drivers anon; unless they happen to be included within the defaults sets in the '98 itself. Initially you will be able to set system up using default vga drivers; and then go on-line etc. to locate the more advanced/complete set for the graphics card.
installing '98 (and also ME)...
Remember that once you delete XP you have in effect a "new" blank drive... And thus the comments in the above links apply equally so.