After discovering errors on my computer I deicded that it is better to format drive C and install win98. First I made a startup disk, formatted partition C, loaded system files by using SYS C command and when I tried to install windows through my CDRom, I got the message that "largest executable programme size is 442000 bytes". I tried to use memmaker but could not find it. What should i do?

Did you boot from a diskette (with CD-ROM support)? If so, then you can try the following:
Copy the CD-ROM Installation contents to the C:\ drive:
Assume your CD is E:\
E: press <Enter>
XCOPY \WIN98 C:\WIN98 /S ..press <Enter>
Exit and reboot to C:
delete any AUTOEXEC.BAT and CONFIG.SYS files on C:\
Type CD \Win98 and press <Enter>
Type Setup

Make sure any BIOS virus protection is turned off before you do this.

You should be good to go

Don

Teemo
Check HERE

If you have formatted the the HDD and transferred the system files to the formatted C:Drive to make it bootable and then, after removing the Win98 Startup disk and changing the First Boot Device to CD-ROM drive in the BIOS setup, and restarted the PC with Full version of Win98 CD in CD-ROM drive for it to start the Setup, or if the Win98Boot Disk is properly made to access the CD-ROM drive, then accessing the CD-ROM drive by typing its Drive latter designated by the Boot Disk [one letter beyond the usual letter in Windows. D:->E: ]and then typing Setup & ENTER you must be able to start the Windows98 Reinstall on a properly formatted helthy HDD using a Good Full version Win98 CD and the correct Product Key.

If you can expand what you actually did when you " tried to install windows through my CDRom", we might be able to say what the problem could have been.