I hope this is the right forum, please forgive me if I am in the wrong place

My disk space is filling up fast on my site, and the cause seems to be some sort of log or dump file being generated two or three times a week - although sometimes twice in quick succession. THey are all called core. followed by a 5 digit number.
I guess my questions are
1) Any ideas what is causing this and how I can stop them ?
2) Is it OK to delete them?
Thanks in advance for any help
DG
The site information is as follows
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Cms Version: 1.5.2
Installed Modules:
CMSMailer: 1.73.14
FCKeditorX: 1.1.0
MenuManager: 1.5.3
ModuleManager: 1.2.1
News: 2.9.2
nuSOAP: 1.0.1
Search: 1.5.2
ThemeManager: 1.0.8
Calendar: 0.7.7
FormBuilder: 0.4.4
Blogs: 0.3.3.1
Uploads: 1.3.0-beta3
HitCounter: 1.0.4
FrontEndUsers: 1.6.3
CustomContent: 1.5.2
FileManager: 0.4.3
Printing: 0.2.6
TinyMCE: 2.4.11
Play: 0.5.2
Guestbook: 1.1.10
Banners: 2.2.1
Smileys: 0.2.0
CGExtensions: 1.15
CGSimpleSmarty: 1.4
Captcha: 0.4
Comments: 1.9.2
Forum: 0.9.2
AjaxMadeSimple: 0.1.6
NFS: 1.0
Polls: 0.2.0
SelfRegistration: 1.2.2
NMS: 2.2.2
Album: 0.9.3
Thumbnails: 0.1.1
Config Information:
php_memory_limit:
process_whole_template: true
max_upload_size: 2000000
default_upload_permission: 664
assume_mod_rewrite: false
page_extension:
internal_pretty_urls: false
use_hierarchy: false
Php Information:
phpversion: 5.2.4
md5_function: On (True)
gd_version: 2
tempnam_function: On (True)
magic_quotes_runtime: Off (False)
memory_limit: 32M
max_execution_time: 120
safe_mode: Off (False)
session_save_path: /tmp (1777)
Server Information:
Server Api: cgi
Server Db Type: MySQL (mysql)
Server Db Version: 4.1.22
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