The file "xxx" is stored on a disc named [something cryptic]. Please insert this disc.
If you see this message, chances are you're inserting clip art into a PowerPoint presentation or other document. Or trying to, at any rate.
It may ask for a disc called O9PRMCD02 or O9PROCD02, meaning that it wants CD2 from your Office 2000 Premium or Office 2000 Pro install set respectively.
MSKB article Q235848 has the full scoop on this, but the short story is that not all the clip art is installed on your hard drive by default. Most of it's left on the install CDs to save space. When you choose one of these not-installed bits of clip art, Office asks for the appropriate CD (although in very cryptic fashion). Here are the human readable equivalent names so you can sort out what it's asking you for:
CD VolumeName =================================== Premium (CD1) O9PRMCD1 Premium (CD2) O9PRMCD2 Photodraw Disc 1 (CD3) PD001CD1 PhotoDraw Disc 2 (CD4) PD001CD2 LPK (CD1-8) O9LPKCD1-8 Office Res. Kit O9ORK Pro (CD1) O9PROCD01 Pro (CD2) O9PROCD02 Standard MSOFFS9 SBE MSOFFSBE9 Access MSACCESS9 Excel MSEXCEL9 FrontPage MSFP9 Outlook MSOUTLK9 PowerPoint MSPPT9 Publisher O9PB or 09PBDCD2 Word MSWORD9 PIPC MSPIPC9 MLPK MLPK_
The Volume Name is the label that appears in Explorer next to the drive icon when you insert the CD or the label that appears under the CD's icon in My Computer. Note that the volume label might be e.g. O9PRMCD01 rather than O9PRMCD1.