1---Well let's see. Assuming that it's the: Dell dimension 2400 2.8 GHz, pentium 4,1 GB of pc2700, ATI radeon 9250 pci 256 mb Computer. This is a list of drivers you will most likly need. you probably won't need drivers for your: hard drive, cd\dvd drives, mouse\keyboard, or floppy drive (If any).
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For your ATI radeon 9250 Video card:
1---Go to:
www.ati.com and go to the drivers and software section.
2---Choose Windows 98 Drivers and Software.
3---Choose the RADEON product type.
4---Then choose Catalyst Windows 98 / ME - Driver Download.
5---Download the: Display Driver Control Panel driver.
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For any other drivers go to
www.driverguide.com you need to register but it's free. you should need drivers for you sound card, printer,(If any) Scanner,(If any) PCI Modem, Networking card and Maybe USB ports.
If you want to post a list of your hardware I can find the drivers for you.

One way to find out your Hardware if to go to the Device Manager located in the control panel, then Administrative Tools and finaly Device Manager
2--- Assuming that you don't have any files that you want any more I would choose "yes I want to delete this space".
3--- But keep in mind Microsoft has discontinued support for Windows 98\98SE and Windows ME as of July 2006. so no new security updates will be made for them. and if you have a problem there is no Microsoft Tech support to call.(you'll just be stuck with us at computerforum

).
Also there is a max. hard drive size of I think 128GB or the partition has to be 128GB or smaller. and the RAM has to be under 1.5GB
Plus some new programs coming out won't run on 98SE.
please fell free to correct me if i'm wrong about any thing.
best of luck.
-----Joshua