Help with ThinkVantage "Back Up Now"

[salin]

I use an external HD for backups, but wanted to also use the ThinkVantage "Back Up Now". I just tried to use this feature and I got this message:
C:\RRbackups does not have enough space available to accommodate the backup.

I really don't know what this is telling me. Can someone give me some hints please.

T500 2.53GHz 1.98 GB Ram XP Pro SP3 (used space 87.4 GB)

Let me know what other info you may need.

Thanks

[salin]

I called Lenovo support about this issue. They said I did not have enough HHD space available to do a backup. I have a 160 GB HHD, and I've used 87.3 GB.
Does this seem right?